Honestly she was probably denying the fact that she's a lesbian and broke up with you when she realized she couldn't keep denying it. Im not sure how old you both are. But my guess is her parents are probably homophobic. I doubt she intentionally meant to hurt you, she probably thought that maybe if she dated you she wouldn't be gay anymore. Its not uncommon for someone who is LGBT, especially someone who is in an unaccepting family, to try and force themselves to be straight or deny it before they finally come to accept themselves.
Also ignore what others say. Its possible she may of told her friends she was questioning herself about being into girls. But when she dated you she may of thought she could still be straight or bi. Also other people, even friends, can make up assumptions and rumors about people.
okay well what about the length 7-8months couldn't she of figured it out sooner? Not necessarily, since she still wants to be friends with you she does care about you. And she likely confused those feelings of caring for you as romantic ones. She likely didn't fully realize it until she developed a crush on the girl who is currently dating and the light bulb went off in her head as she realized what actual feelings of attraction are.
But still, she hurt you. You don't owe her friendship and she doesn't owe you an explanation. Its probably best for both of you if you move on your separate ways. If you really want her to talk to you about why then you can't come at her mad, you have to cool off first and be ready to listen to her story. If you really want to know you need to give yourself a break first so you can heal from the heartbreak. As for people asking you about them, if its your friends be honest with them and tell them you would really prefer they don't mention them. If they aren't friends tell them you don't care, they are doing it to get a rise out of you bc they know its a sucky thing to go through. Don't give them a reaction and eventually they will get board.