In short, they can't stand her.
Desperate for a promotion, she is given one last chance to prove she can work with others.
When she is sent out of town to track down a drug kingpin she crosses paths with Boston PD detective Shannon Mullins (McCarthy).
Mullins is hard-nosed and down to earth and she protects her patch with her life. She is not going to let Ashburn stroll in and take over.
After a series of early skirmishes, they are ordered to work together to find drug kingpin Lassen.
And so the fun begins. Mullins slowly breaks down Ashburn and the two do what they must to get the information they need.
It is here that some of the funniest scenes take place.
Complicating matters is Mullins' family, who have never forgiven her for arresting her brother on drugs charges.
Now on bail and seemingly mixing in the wrong circles again, he complicates Mullins' pursuit of justice and the drug bad guys.
Directed by Paul Feig, there is a real Bridesmaids flavour to The Heat.
If you can put aside the never-ending profanities that flow freely from the mouth of officer Mullins you are in for a treat.
Her off-the-wall humour and straight-shooting style leave you never knowing what's coming next.
But you can be sure of one thing - it will be funny.
The Heat
(R13) 130 minutes
Rating: 4 / 5