Healthy weight?? Slowing down for winter??

[NinyaCap]

Hi guys,, my garter has been skipping the majority of her meals now that it's cold outside. The last time she ate was about a month (maybe more) ago which was a large piece of f/t silverside. At night her temps drop down to the mid-upper 60s, I was wondering if you think this may be too low for her. I'm thinking she's holding her weight pretty well, but I still have my worries so a second opinion would be great! (photo attached) Any advice on getting her to take/anything at all would be much appreciated. I've been a huge worry-wort over this baby for awhile now! Thank you:))