if you dont experience constant dizzyness or lightheadedness, its fine
your base heart rate doesnt really measure how fit you are, as it can be genetic and have many other factors, if you want to compare, you and a sibling get your heart rates up to about 170 (cardio) and measure it 1 minute later to see how fast it went back down, those are the numbers u want to compare
also a base rate of near 100 should be medicated, its too high and shes at a risk of tachycardia, which is basically a heart attack, although you probably want to see a doctor about that, blood pressure might be off, etc