My .02 says to keep the house at 65, go enjoy your vacation far away from the frozen NE and let your friend take care of the heat. Just how much do you think you are going to save, vs a potential freeze-up......broken pipe situation? The short dollar says to go with 45 degrees, the long dollar says "why take the chance".
I was in a condo late today that they couldn't shut off the shower valve. Yes, people live in it, but don't use the upstairs. It was 74 downstairs, 28 upstairs. Toilet was frozen solid, shower valve had the guts pushed out into the shower itself. Even shutting down the water was difficult....older folks still live there. Shark-bite ball valves.....done......heat is back on, but you can't imagine the repair costs that will follow.
Total electric baseboard in these homes....individual thermostats.......easy to close doors and turn off the heat....
Even if your home is fairly new, 45 is a close call when the wind blows at 40 mph overnight. I wouldn't even consider shutting it down either. Trust your maint guy, and sleep peacefully. Also, the poor AA would be sad to not get to stretch her legs on the cold nights. The structure of the house will thank you later, also.