Okay dude, listen up.
Odds are you got played, period. Now of course there's a chance you didn't, but it's a small chance.
Think of it this way....she was "guilt tripped" into going?!?! WTF kind of excuse is that, and what kind of man are you for buying it. No, I shouldn't say that about you, I understand why you're buying it, been there, done that.
Her pulling that card was her way of saying "Look, I know what I'm doing is making you uncomfortable so instead of saying I'm just going because I want to I'll shift the blame so if the sh1t hits the fan later I can use that as an excuse to not be held responsible.".
It's passive aggresive BS man, pure an simple. If she truly didn't want to go she wouldn't have. Based on what info you've given it's clear to me that she really wanted to go all along but that she likely thought to herself "If I tell him that it'll likely hurt him.".
As for you going/not going, let that crap go. As someone earlier said, you can't be with her 24/7, so going with her to "keep something from happening" isn't going to do jack squat. Even if you'd gone and blocked something there will ALWAYS be a next time, and you won't be there every time. Besides, it really shows you don't trust her. If you think about it you're going would have been for motives other than that of what you told her you were going for and that is deception whether you chose to agree with me or not.
Oh, and if she wanted you to go she would have found a way to make that happen, but she didn't. that right there speaks volumes.
I have a very good friend who I dated about a year ago or so. We've remained close friends ever since and she calls me3-4 times a week. She's dating right now and has been with this guy for a few months. Before him she'd go hang out with me if I asked her to. Now, from the very start of her relationship w this new guy, if I ask her out as strictly a friend she'll either invite him along or decline. I don't like him for the simple reason I think he's not good enough for her (25 year old stoner slacker living with his mom and no drive or ambition to even get a basic job, and she's a very driven person) so I always say "No, leave him and come hang out with me/us.". I've done my best to "guilt trip' her into coming out without him and she just won't do it, which was rather unexpected. Whether I like this guy or not is irrelevant, what's relevant is my admiration and respect for her for sticking to her principles and not wanting to cause harm in her relationship. No matter how much longer I've known her before this guy she's with, the simple fact is she's WITH him and she doesn't want to do something that would make him uncomfortable.
The odd thing is, she's pretty sure she won't be with him much longer (her own commitment issues/ she knows he's not "the one"/ she realizes he has no drive or ambition to better himself). Yet as long as she's with him she'll treat him with this respect. That's fvcking rare nowadays.
I have mad respect for this girl now as a result.
I guess the point to all my babbling is this.....here's what I'd do:
Say "Look babe, you know I really like you and I really would like for our relationship to start heading in a more commited manner. I think you want that too. (now assuming she does, go on) So I just want to be clear that I want to trust you in the future, and I do now (which you really don't, but I suppose a little white lie here won't hurt) but if we're going to "get serious" I need to tell you I'm going to have a hard time dealing with situations like last night."
Gauge her reaction from there. If she says she's not giving that sort of thing up, or bringing you along every time in the future then it's up to you to decide to stay or walk. If I were in your shoes I'd tell her (assuming she says she's not giving anything like that up) "Well, I'm going to have to ask that we just remain friends then.", and STICK to that. There's a good chance she'll walk away and not come back. If she does, she didn't really want you that bad in the first place. However, if you offer her something(s) that she decides she just can't live without/or adores about you, then she WILL be back, relatively soon.
Sorry for being long winded, I'm stuck at work today and don't want to be. Anyway, I hope at least a few of my words help you dude, good luck!