just finished a re-watch since it was on HBO ... this movie still holds up really well and can actually be looked at a little differently as relationships have changed in modern times.
way back when this first came out, I (and a lot of people) assumed Tom & Summer started their "relationship" from the same foundation, both singles at an office, completely carefree in the world.
But, it can be argued Tom was essentially an office sidepiece for Summer and she always had the other guy asking her to be married in the background ... and he wasn't just some perfect-moment-guy for Summer that came thru only after Tom/Summer broke up.
On this re-watch, I noticed they only did Tom stuff during their happy phase, she only lets him get to her apartment after months of hanging out, and she only really introduces him to other people in her life at her rooftop party after she was engaged.
She basically had him as a sidepiece and indulged his crush since it got her away from her actual normal life. One of Tom's biggest flaws is his selfish focus and it really killed him here ... if he actually asked Summer more about her life, friends, interests ... maybe she would see him as more than just a sidepiece or she'd give up the jig and let him know he's a sidepiece.
That being said ... no matter the angle you look at it, she still a savage for inviting him to that rooftop party w/o letting him know what's up before hand.
I mean she did say she wasn't looking for anything serious in the beginning. Tom just caught feelings. 
