Search Results: asking a girl out to lunch

I have been friends with this girl im interested in for 3 years now. Last year she hinted at wanting me to be her boyfriend one week, then we matched on tinder the next week. The trouble was I had a cancer scare that i didn't tell her about at that time. I wasn't about to ask her out and then say "oh by the way, I have cancer". Turns out everything was cool and im cancer free. However, by the time i got this news, she had a new boyfriend. Fast forward to this fall, she was single and we hung out one night. she was telling me that her friend was trying to hook her up with his friend. But at the same time she was very flirty. Ever since that night I've been trying to hang out with her more but she always has something else to do like HW and work (she is a workaholic). She invited me to hangout with her and her friends one night and that was cool. (was she seeing how i would be around her friends there?) But since then, every time she has seen me around, she'll make a point of coming up to me. like the other day she was out on a run and spotted me walking to class. She made a point of texting me and coming up to me after. I can't help but think that means she's still interested and single begging for me to ask here out. Trouble is, as before, any time is ask to meet up to ask her out she has something else. Like tonight I texted her asking to meet up for lunch tomorrow, but she replied after 30 minutes (she usually is very quick to reply). In that reply she says she literally just made plans. Is she just not into me anymore? Is she playing hard to get? I'm confused.
I also have no idea how to even ask her out. Im scared to incase it makes the friendship awkward.
I also have a tendancy to overthink things because of my anxiety.