she didn't really turn him down, though. she just said she wasn't ready, and he wasn't willing to wait. they were only 19, which is honestly too young for a lot of people. i don't see why that makes her the bad guy. lucas should've waited for her since she's clearly the love of his life. instead, he dumped her and made lindsay his rebound. i really don't get why only peyton ever gets blasted, when it's lucas who really owes it to his gfs to be faithful.
Okay, so Peyton turns down his proposal and doesn't fight to stay with him. She acted like a victim, like ALWAYS, and SHE gave up too. She let him walk away. I agree, 19 might haven't been the best age for him to propose, but at the same time, getting engaged isn't getting married right away either. He was hugely vulnerable when he went to see her, after only seeing her few and far between after she left town. She could have accepted his proposal and suggested they wait, LATER. And ultimately, I think she's had more than enough chances to be with him. He's messed up some of the time (and you're right, he always wants to talk out of both sides of his mouth and play both sides, or cheat, or just be moody and isolate himself entirely) but I don't think Peyton knows how to be an equal partner in a relationship. She's always the victim, always expects to be saved, and never really seems that into it.

I don't think it's really fair to call Lindsey a rebound. That we can't be sure of. Sure, he had just gotten out of a relationship and might have gone in to the relationship early on because he was lonely or whatever, but his intentions in being with her could have and probably did develop into something else (a la Nathan and Haley). I see genuine loved shared by BOTH Lindsey and Lucas. They seem very much compatible, and much moreso than he and Peyton.