Trying to quote multiple posts on mobile is a pain in the ass so in response to your first post...
Why the f@ck would you ask to see her again? This may come off a little harsh but I'm genuinely...maybe not confused per se, but I just don't know. Making tenative plans if it comes up in conversation in person is one thing, asking over text RIGHT AFTER hanging out is another entirely. And I mean that in a bad way. You might be thinking, it seems nice, what's so bad about it?
*It implies that you didn't think you were already going to see each other again, which shows a lack of confidence.
*It's farking needy. Even after I have sex with a girl the first time, I text her like normal (Hey boo ) like a few hours later and then say early on in the conversation "Just wanted to tell you I had a great time last night. *some kind of compliment here about her appearance...I've heard you should compliment her sexual technique too but I have yet to find a way to integrate this smoothly and keep it from backfiring and sounding pervy*.
NOTE: It is not always true that you should be the one texting her first. That's very dependent on the relationship, the stage you're at in that relationship and the value you two place on each other. But for now, as a rule, that's how it should be. And remember, all the rules of PUA are really mroe like guidelies. Confusing, I know.
To directly answer your question...send her something similar to this text and then take my tips from above and start applying them IF she responds to this first text. If not, re-visit your relationship with her and consider the circumstances once you've been with a few other girls...OK, here's what you say "Hey, I've been crazy busy with (school, work, whatever the f@ck it is you do) and I haven't had a chance to talk to you lately! What are you up to?" DO NOT DO NOT DO NOT apologize. So many people apologize out of habit because they were taught to be non-confrontational in middle school, which is a way of avoiding liability for bullying lawsuits but has emotionally cripped an entire generation of young adults. Save apologies for whe they're merited! Urbancowboy out!