Why do you have a crush on a woman you have barely talked to? Do you mean that you are in lust with her? (which is much more acceptable than being in love with, considering you've barely talked to her)
Also, while it's good know about what signals she's giving off - do you know what signals you are giving off when you speak with her?
In relation to the handshake - it's not possible to politely shake someones hand without turning fully towards them. Anything else comes across as supremely disinterested, and is considered rude. Many women won't do anything to purposely hurt someone who hasn't given them any cause to hurt.
In relation to the other body language - it wasn't particularly interested, but it wasn't negative either...so you can try again (there was nothing in there that you described with is 'dismissive')
If you know (or can find out) what kind of coffee she likes - why don't you take her one (with a cup for yourself of course).
One good way to overcome anxiety is to practice. In this case, as it's approach anxiety you have....you can make it safe by practicing body language as you speak, while imagining approaching someone.
On the the things about our mind is that it can't truly distinguish between imagination and reality. If you imagine approaching her, looking in her eyes and saying the words...you should find that your heart rate starts to increase, your voice may crack, you may crane your neck forward, you may stutter (or just not say the words at all like you would like to). Practicing helps
reprogram your mind.
What you practice you gain confidence in doing...if you think about it - this is the same for any skill you possess. The mind skills are a bit more difficult because they are so much more complex, but when it all comes down to it, they follow the same basic rule...the more you practice, the better your confidence will become in what you practised.