What's the best way to stop talking to someone without hurting their feelings or ignoring them?

Okay. There’s this girl I met from a dating site. She seemed really sweet, nice, and funny. She’s very encouraging and often compliments me, even though I don’t ask for them or set them up. I made it clear online I’d like to find someone to DATE. I don’t mind friendship, but she very clearly didn’t talk to me as if we were buddies. Even though she’s not my type physically, she seemed very flirtatious and promiscuous (or so, I thought). And since looks aren’t the most important thing to me, I thought maybe we could’ve been a couple.

But yesterday, I find out she’s attracted to women. I’m kind of upset because I thought there were clear signals she was into me. Apparently though, she’s into girls. So there’s no future, here. To make it clear, I didn’t want to just “sleep with her.” I thought she wanted to pursue a relationship. I thought she was straight, considering that’s what her profile SAYS. I’m upset because I feel lead on. I’m not sure if we could stay friends, and I honestly, don’t want to after this. What is the best way to break off contact with her without hurting her feelings or ignoring her?

Whoever chooses to answer, please, STAY ON TOPIC. Thank you.