It’s probably too sensitive? Have you tried stimulating it indirectly, for example by licking/touching its hood right above it instead?
Also, take your time, listen to the body language and if you sense some kind of positive response you keep doing exactly that, you don’t change the pace, pressure, angle, etc.
Sorry I couldn’t help. Ultimately, communication is key and if you’re both satisfied and she doesn’t feel she needs more or missing out, then there’s no harm :)