Women don't *want* to lie to men when turning them down. They have to, for their own safety. If a woman asks five men to leave her alone, one will politely do so. One will get nasty and leave. One will get nasty and refuse to leave. One will issue rape threats. And one may get violent. So yeah, they'll say whatever they have to, to get someone to just leave them alone.

She didn't owe you a reason in the first place. Accept the rejection and move on.

Honestly, the biggest problem here is that apparently she felt she had to claim to be a lesbian so that you would take her rejection with grace. Whether or not that's because of her previous experience rejecting guys in general, or specifically because of you, it's still a pretty sad state of affairs. At any rate, as the others here have said - "No" should be enough. You're not entitled to have a shot with her, regardless of her orientation. Nobody's obligated to date anyone they don't want to - Regardless of if the reason is "good" or not.

Maybe the thought of sex with you drove her to temporary lesbianism. It's a thing, look it up. When you get rejected, move on and don't look back. There's someone who will find you tolerable -- you just need to go find her.

Looks like you hassled her to the point that she had to lie to get rid of you. Her life sucks. You need to let up and learn to respect women and take no for an answer. That scene in star wars where the guy is hassling Carrie Fisher and she's saying no, but after he keeps hassling her for ages she finally gives in and kisses him back passionately? That was written by a jerk who thinks you have to just keep hassling women till you wear them down. It doesn't happen like that in real life.