Dude, end it now before you get in deeper. She lied to you, and she's still talking to a guy who has feelings for you. NOW is the time to leave, when it's not going to hurt. Who cares if she's trying to let the ex down softly? She's lying to you about time she's spending with other guys who have feelings for her.
Don't wait till you catch her red handed, come on!!! You have plenty to go on here to know it's not gonna work, why waste your time?
I don't get when people do this, stay in something that is pretty much doomed to fail. I'd rather be single than let something die out slowly or waste my time with someone who doesn't respect me as she clearly does not you.
But I digress... as I always say to my friends - It's your life and you are the only one who has to live with your choices...if staying with her is worth it to you, then I'm pretty much blowing hot air, here. But follow your gut. Don't stay for the wrong reasons.