If you cannot trust said girl to be discreet about this minor anomaly, then you certainly should not be involving her in any exposure of your genitals in the first place, should you?
Or is this the way sex works in your school - an exhibition sport - "look what we did" - "can you beat this"?
Don't sweat the smegma. She almost certainly has it as well - I wonder how she deals with it? When (if) you get to see her "bits", do take a close look in the folds and see how much she has. It's quite interesting.
Do read - heavily - through the discussions here. You need to learn how much a tight foreskin does (not) matter for various sexual activities, and that the sensitivity you describe is actually a very good thing.
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