I don't think it would affect her temperature so much. Mine were 36/37 weekers both born in early spring/summer, and we ran the heat the first couple weeks. I'd keep her layered really well with a onesie under her clothing, socks on her feet, a hat (or two) on her head, and tightly swaddled. Ours stayed pretty toasty that way. We never warmed formula so that they didn't get used to it and refuse room temperature; it made it a lot easier when we were out. That said, it certainly won't hurt to warm it if that's what you want to do instead.