A.S.
I would get her checked for a bladder infection. We had a fever with our youngest when she was 10 months old that was only a fever. It lasted a week and while I chalked it up to teething it turned out to be a bladder infection. I took her in and had her on meds, they were the wrong ones for her (a fluke problem) and didn't work and she wound up with a kidney infection and septicemia, serious stuff that had us in the hospital for 9 days. Our pediatrician said that some bladder infections show no other symptoms but the fever.
Please don't leave it, she needs to be checked out by someone. My daughter has had to have multiple tests since because this could have caused perminant damage to her kidneys.
Let us know how it goes.
ps. As far as I know heartrate does increase with a fever because your body is working hard to fight the infections.