I'd be reluctant to take a trip without meeting somebody. Especially, given the circumstances here. My alarms are going off. So, don't do that for sure :O
That said, she's kind of jerking you around. Now, you have to use your judgment based on the particular facts of the situation. One way to handle it is an ultimatum: "look I've had a lot of fun talking to you, I think you're great, but I'm not willing to take a trip with someone (don't say you... say someone, anyone) unless we've met in person at least a couple of times. so let's meet up, have a drink, it'll be fun" It has to be presented in a very non-confrontational manner, not in some aggressive ultimatum. do not act frustrated. This is probably what I would do because I hate playing games and being jerked around. I'd be pissed if someone kept canceling on me last minute.
Ignoring the trip for a moment, what you can't do is keep letting yourself getting jerked around (and that's for reasons of self-respect, and beyond just from a PUA point of view). Unless of course you're content with phone sex. but don't discount the fact that she has someone else's portfolio of pics and is a fatty with a sexy voice
You gotta put your foot down. the two options i see are an ultimatum, or distancing yourself. no more phone sex, short answers of POF, if any. why? because you have better things to do then get blown off. other women want you and won't play games. there's hard to get, which is understandable. then there's being inconsiderate, which is what's going on here.but honestly, I've never encountered anything close to this situation. I would have cut her off after the first blowoff, even if she was hot. but that's me and I hate hate hate those kind of games. maybe someone else has better advice.