I don't think she had a nose job because ...
1. She was younger in those pictures posted above, people's facial features change as they grow up. I didn't have a bridge and the tip of my nose was very round when I was 14. Fast forward to my last year of high school, I suddenly have a bridge, which in turn kind of pulls up the rest of my nose and causes my tip to be less rounded. The change is really noticable, especially when you look at my profile.
2. The way they did her makeup could change the appearance of her nose. Debra Messing has a really long nose that comes out a lot, she says they put light powder on the tip to make it seem shorter. I'm sure there are makeup tricks that can do the same for making the tip rounder/narrower.
3. Like someone mentioned, she constantly posts in her Nexopia, if she had plastic surgery we would have noticed like, "What? Why does it look so different?" But obviously we haven't, because the change in her nose has been gradual/natural.
4. She's a model who JUST turned 18. I don't really see an 18 year old messing with her face like that, especially since she is in a business where her looks matter. What if they botched up her face (like Michael Jackson)? Her career is gone. I don't see any model risking her career like that.
That said, the picture with Angela Lindvall is pretty damning... but Heather has always had a bump on the right side of her nose, example:
http://img7.imagevenue.com/view.php?image=97947_CHAL10_201538_pih_122_464lo.jpg . It is just not so prominent in that shot because it's frontal, not side/frontal. If she did get a nose job, why didn't she fix the bump?
Anyway, I think we need more pictures before we can say anything concrete. Is this the only shot that leads us to believe Heather got a nose job?
And wow. OT but Angela looks so old in that shot. And why no pics of Caroline/Heather? I thought we'd see pics of them goofing around backstage at VS since they're such good friends.