Many girls love being pursued, it validates they're of worth and generally makes them feel good (who wouldn't feel good having someone pursue them, provided they aren't a stalker or the pursuer has 0 value to them).
It's tough to say what her motivation is. On the one hand interested girls will offer an alternate time to meet if one you'd presented doesn't fit their schedule, on the other she may very well not have the time to go out between work and school (and whatever commitments she may have). Further, there are some girls who don't want to start hanging out with a guy because they may feel too vulnerable, or quite simply that they are determined to attain a goal without having any distraction (emotional investment in getting involved with someone new). The reasons may be any combination, the point is we don't know.
As the guy above said, you need to be less outcome focused.
You recognizing that you're developing one-nittis is a good thing, as you can now do something about it (e.g., game other women). It's always best to keep one foot in reality rather than jump both feet into fantasy (you don't really even know her apart from idle chit-chat at the coffee shop).
What I'd do is wait a week or so and then contact her again, have a plan. Don't be wishy-washy, rather assert yourself telling her you know of this awesome trial you've been meaning to try for some time and that she must join you, for example. Honestly, I'd probably do something more low-key for the first meet, but that all depends on the type of girl she is. If she's a high energy party girl, then find something high energy (carnival, concert, etc.).
Don't take her not giving you an alternate time to meet as a lack of interest. I'd probably make a point of not going to the coffee shop so much if you are already, that way she'll wonder a bit about your whereabouts. Contact her out-of-the-blue in a week or so with something funny, and/or random (here's some text msg openers if you aren't very creative
1-vt21175.html?postdays=0&postorder=asc&start=0).
In the mean time create opportunities with other chicks, but ultimately the best way to GET your one-nittis is to sexually escalate with her but in the mean time you're going to have to slow your roll and work on your frame state (you're too gung ho over her right now, having other girls on the side will help you operate from a frame of confidence rather than one of neediness).
Game on gamer!