Kids snoop, it's in their nature. They want to know what's going on in our lives, they look at us as role models, and they're not stupid. They know that all the "interesting" stuff goes on when we're trying to hide it from them.
I think it's important for parents to be honest with kids who are mature enough to understand it. The fact that the teenager is approaching you and asking these questions is proof that she's trying to understand it.
Kids learn behaviour from the behaviour of their parents, NOT how their parents TELL them to behave. If your kids realize that you're hiding / lying to them about your feelings, what do you think they're going to do about their love interests? Do you want them to keep that information from you?
“As I am sure any cat owner will be able to tell you,
someone else putting you in a box is entirely different
from getting into a box yourself.” —bisexualbaker