Little bit long, but please read!

I brought home my first ball python about 3 weeks ago. She's about 6 months old. I brought her home on a Thursday and the breeder I bought her from was feeding on Sundays so I left her alone for the weekend and fed her on Sunday (seemingly without a problem). She didn't strike at the rat, she just smelled it and kind of ignored it at first, but when I put it in her tank and left it there she bit into it and ate without a hitch. I checked her tank regularly when I was changing her water and such to see if she regurgitated but everything was always fine. I keep her temperature at about 86-89 in the day on the warm side, and bring it down to 75-78 at night. I use a UTH on a thermostat and no heat lamp in a 15 gallon tank, the pad covers about a third of the tank. I always keep a damp towel over half the screen cover and the humidity usually stays at around 50-60%. As far as I know, she is warm enough, and it's humid enough, but the last two Sundays when I tried feeding her she wouldn't eat. When I prepare the rat, (I'm feeding f/t) I put it in a bowl with boiled water for about an hour, and if the water is cool enough I usually put new hot water in the bowl to warm up the rat. It's always soft all the way through when I feel it, and I dry it off before I try giving it to my BP, but she still wont take it. She doesn't even seem interested anymore, she wont smell it or come near it, and even when I put it in the tank and leave it, when I come back an hour later to check the rat is still there and she's off climbing her branch. I have only handled her twice in the 3 weeks that she's been with me, and that was only to move her to a container while I changed her tank. I have no idea why she wont eat, and the last thing I can think of is that maybe the rats are too big, she's eating pups but they're still only about the same width as the thickest part of her body. Please if anybody has any ideas why she isn't eating, tips or tricks I can try, let me know! I need help!

I've heard that sometimes snakes wont eat for months, especially in the winter, and it has only been two weeks.