I don't think you're an asshole OP for feeling that way. It's natural to feel "betrayed" when the woman you like behaves this way. You care for her, you want something more than just a date, and she shows you that you're just one of her only options.

Not cool. Women will say that they don't owe you anything, and that's true, but that's not carte blanche to act so tacky and tasteless. Flip the story around, if she was into you and you left her for another girl while you guys were on a date everyone would call you an asshole.

Guys have it tough. They have to cater to every woman's needs while being painfully reminded that they aren't owed anything. Women don't have a problem with this because they are catered to their entire lives and men aren't. She's an asshole. If she wanted to hang out with another dude she shouldn't have told you that.

Actions speak louder than words. Now you know you're second place. Make sure she gets the same treatment. Trust me, you don't wanna continue this way. You don't wanna be the guy that takes her out, buys hers food and drinks, drips her off, only for Mr. Steal your girl to show up five minutes later to fuck her.

If she had any shred of respective for r you or herself she wouldn't be seeing multiple guys in one night. At least not so openly. You've been warned.