"We were the only ones there and it was so beautiful and relaxing," Gerster said.
"As we were leaving, I heard a bit of rustling coming towards me and as I stepped into the clearing there she was, Hillary Clinton and Bill with their dogs doing exactly the same thing as I was.
"I got to hug her and talk to her and tell her that one of my most proudest moments as a mother was taking Phoebe with me to vote for her."
Gerster posted a photo of herself with Clinton on her Facebook page. She said Mr Clinton took the photo.
The Clintons have lived in Chappaqua for almost 17 years. Clinton cast her vote in the very town on Wednesday.
I do wish I asked Secret Service to take one so he could be in it," Gerster said.
'She hugged me and thanked me and we exchanged some sweet pleasantries and then I let them continue their walk.
"Now, I'm not one for signs but I think ill definitely take this one. So proud."
It appears Gerster is no stranger to Clinton, bumping into her before. She posted an older photo of herself and a friend with the politician just days before the election.
"Back in high school...at a fundraiser my mom hosted at the Kittle House. (Clinton) was the guest of honour," Gerster wrote.