Teeth, new cognitive developments, viruses and time changes could all contribute. I agree with another poster that your house sounds very warm. I keep my thermostat at 68 degrees during the sleeping hours and my kids, esp my daughter, are still warm enough...in fact she sleeps in shorts and a tee shirt and she will not sleep with a blanket, only a sheet. I know when my kids were little I was constantly worried about them being warm enough and I frequently found them to be most cranky when I had overheated them, night or day, sleeping or play. For me, I hate waking up sweaty and I also hate being super hot while socializing, shopping, etc...
Also if her bedroom is on the second floor it likely to get quite warm.
Best wishes for a good nights rest for your little one!