She just got married. She'll be busy, so you probably won't be as close as you were before (especially because of this incident). As hard as it may be, be the "bigger person" and drop it.
Definetly don't act on your feelings right now. You'll end up doing something rash and dramatic and you'll regret it later. Don't vent to anyone (in real life) because girls talk, and never call her or text or whatever when you're angry. If you really want to see how she feels about everything you've done for her, some other time, when you're emotional, casually mention something about the shower or reminisce, and see if she remembers to thank you or if she says "yeah it was beautiful" or whatever. It sucks when acts of kindness aren't appreciated, but whatever. You live and learn.
I know it's hard, and she should have been a bit more appreciative, but try to make excuses for her; you never know what's going on in her life or what she's thinking. Bringing up her past mistakes does nothing. You might feel better about yourself for a second but it's petty.
I don't want that to sound mean, so here are a few more
Like others have said, try to be a nice person (without being a push over), never end relationships on bad terms, and keep your expectations low. You'll be happier that way. And being a goody-two-shoes and pious might seem boring, but at least you won't regret anything in the long run.
In my 19 years of living, I realize now that I was happiest when I had the fewest number of friends. I hate to say it, but girls are so...