Why is she bothered by this?

So my gf is really bothered that when i was 11 yrs old, i touched my neighbor and kissed her all the time, she is still my neighbor and i rarely talk to her, i dont care about her at all, i told my gf this, and i feel like everytime she asks me something about her i have to lie so she doesn't get mad I also liked my neighbors cousin, which also bothers my gf. What should i do, she is always busting my balls about this?