Next month will mark 62 years since she arrived in the house, near the lake's south shore, after moving up from Invercargill.
"I'm not into the science of it," she declares.
"You've got all the experts doing that. The only thing I feel is the rising and falling of the lake."
The lake's rhythms have been out of whack for years.
Algal blooms have worsened since 2006, turning parts of the picturesque lake a reddy-copper colour.
The declining water quality is not just visual - it has led to fish kills and skin irritation for swimmers.
The alarming decline prompted the creation of the Friends of Lake Hayes lobby group, which commissioned freshwater scientist Marc Schallenberg to produce a report on ways to nurse the lake back to health.
That report is central to the Friends of Lake Hayes' plea to the Otago Regional Council for a clean-up plan.
The report notes a drop-off in annual "angler days" at Lake Hayes - an indication of lake health.
In the mid-1990s and early 2000s, it averaged about 1500 cumulative "angler days".
But trout scarcity and the lake's algae-infected muddy brown colour mean that dropped to a record low of 180 days in the 2014-15 season.
Kerry Dunlop, who lives at Quail Rise but whose family built a holiday house at Lake Hayes in 1953, is the Friends' chairman and a keen angler.
"When I used to go fishing, I'd row across the lake, trawl out the line in the rowboat, and you'd just about always guarantee you'd get two fish, if you went out for a few hours."
The situation is so dire he did not bother with a fishing licence last season.The last fish Mr Dunlop caught was a trout last spring, well after the lake recovered from summer's blooms.
"It was a beautiful silver fish I caught in September - full of fight."
Dr Schallenberg's report explains why adult perch have become stunted - it is a lack of predators, apparently.
An Otago Fish & Game survey done last year found almost all 70 perch caught were under 20cm.
Mr Dunlop ruminates: "I've only occasionally got a perch that's worth bringing home to cook.
"In my younger days, I used to sometimes just foul hook the darned things. You'd be basically fishing for trout and the next thing you'd catch something - and the perch don't fight much - and you'd have something hooked by the dorsal fin, or something like that."
He slaps his copy of the report.
"This report explains that, I think - gives a better understanding."
It is not just the fish having trouble.
Lawyer Tom Pryde - who brought the ITU triathlon world champs to Lake Hayes in 2003 - has a long history of swimming in the lake, for an hour and a-half or longer.
He has had a holiday home at Lake Hayes for 40 years and has lived lakeside for a decade.
Swimming was a big reason to move.
Mr Pryde: "We've got steps down to the walking track and there's more steps down from the walking track to the lake. It's about a one-minute walk from the front door to the water in your togs."
But then the algal blooms appeared.
"Once the thing starts to bloom, if I swim in the lake by the time I get to the shore and stand up, my nose is running like a tap and I'm sneezing."
The symptoms can continue for a week or 10 days.
"I've given up on it," he says.
"I just can't do it anymore."
He adds: "I'm sitting at home here now and I'm looking at the lake and it's looking beautiful and I just think 'what the hell, why can't I swim in it?'"
Landscape architect Pete Ritchie, himself a keen open water swimmer, describes symptoms similar to Mr Pryde's.
"Watery eyes and reasonably congested, runny nose and so forth, for a day or two afterwards."
These days he enjoys the crispness of Lake Wakatipu.
"Lake Hayes feels a bit more soupy."
Like the water clarity itself - this summer was the best in seven years - the debate about Lake Hayes' state ebbs and flows.
"It's gone on forever," Mrs Strain says.
"I think the lake is better than it was."
She explains that Strains Bay - "our bay" - on the lake's southwest corner, filled with sludge so badly it became unusable.
Her finger stabs at photos neatly stacked on her dining table. One shows a dinghy's motor mired in muddy muck.
On the back, the date is recorded as February 1988.
Mrs Strain recalls quitting her job at the airport, working for Alpine Helicopters, and establishing a business called Go Fishing, giving anglers the tools to enjoy Lake Hayes for a day.
But after a single summer the sludge killed the business.
"There was nowhere you could take tourists down through that," she says.
"I wouldn't have even walked through it, it was so bleugh."
Stinking, stagnant water is still an issue for that area of the lake - in an area of the track near the Threepwood development, before an incline.
Mrs Strain: "When it's flooded, I hardly ever walk that way. Unless I'm going to go right round and then I have to. Yeah, I don't like the putrid water there. The smell I can cope with but I don't think it's good, that's all."
In the 1950s - she thinks 1956-7 - land north of the lake was cleared for farming, sending brown plumes into the lake.
"That happened for about two years."
Back in those days, three creeks entered the lake and the flow was comparatively fast.Not so now. Scientists estimate it takes 1.8 years for water to cycle out of the lake.
"Have you ever looked at the outlet?" asks Mrs Strain.
It has been piped under the state highway, as it turns out, whereupon it becomes Hayes Creek.
Mrs Strain has seen scientific reports and lobby groups come and go, punctuated by periodic water quality testing.
"They're always coming out with something scientific; looking into something scientific. And nothing ever gets done about it.
"But surely in this day and age, it's quite easy to know what to do."
Mrs Strain got angry in 2010 when Niwa tested the lake, installing 10m-long bags to see how much phosphate came off the bottom.
"I thought of all the time and the money. Can't they do something physical? You know, just one thing? Not to spend all that time and money on tests.
"You see, tests have been going on for 50 years. And what have they actually done?"
As always, she comes back to the outlet.
"I've always wanted them to keep the outlet clear. You know, really clear.
"Every couple of weeks have a look and see if there's something blocking it. And keep the lake level stable."
