I was in my 20's before I realized that I was in fact Bi, though it's not about the sex for me. I never really thought about was I bi or straight or gay or whatever. It just wasn't an issue growing up, I just was. I never really had female friends, a few close ones, but mostly I always thought other girls were foolish and pointless. I've always liked boys however, even got in trouble because I was "boy crazy" and they thought it was effecting my grades.
What changed for me was my understanding of "love" and how I love, my life experience and time to mature. I met someone in my 20's who was Trans-gendered and dated them while they transitioned. I realized that I don't care about a his/her "parts", I loved them for who they were, it was emotional and because I loved them I was able to bridge the gap into the physical/sexual with out issue. I love to "give" physically, that's where I get my most fulfilling pleasure. So, as long as I was sure that they felt loved and pleasure I was over the moon.
Your daughter is only 13, her peers (dating pool) is still so immature. She may just need time, she has YEARS before she's old enough to choose a life partner. This is a stress she doesn't need, since you're so open with her help her to realize that there is no rush for her and that no matter what you love her. Help her focus on having friends and not stressing over "dating". I'll happen when the right one comes a long. Perhaps have her talk to her aunt.
Male or female, when the right one is with you, it's wonderful. It is very likely that she hasn't meet the right someone yet. Like I said, she has YEARS yet ahead of her, no rush, have fun.