I wrote up a lengthier response but decided not to post it since I don't feel like debating the ethics of this situation with others. In short, though, I agree with
@efle that personality shouldn't factor into grades. I can also say that I don't think fighting for points is wrong at all in many cases. I remember
@allantois posting once about how in some pre-req labs he'd argue for points that he lost with the TA and often get them back or something like that - not sure if he should be chastised by some of you too for wanting A's in labs.

Every grade counts when you're pre-med, honestly. I just feel like some people have been too hard on the OP possibly.
However, after thinking through it I agree that at this point, there's really no point in arguing over this with the TA. Clearly you guys are already on rough terms; arguing that the other guy got the points undeservedly really isn't going to go over well. I would compare this situation to a sunk cost, OP - there's probably nothing you can do at this point to smooth things over with this TA, so you should basically just avoid crossing her any more than you have to from now on. The situation is what it is at this point. Calling her out, should she choose to dock five points for your being late, will only add fuel to the fire. You, however, probably should've known that the lab wasn't going so hot a month or so ago and adjusted your focus to dominating the lecture to compensate for the lab. And it may be that the TA is more worried about your getting out on time than she is about your getting a certain percent yield. In any case, I would just put up with her as well as you can. I also liked
@bee17's advice, and would encourage you to listen to it.