I got a voicemail today from one of my ex's who i dated for a week but never had sex with.. w/e long story saying "Hey I'm running and was wondering if you wanted to come run with me, call me back when u get this."
I call her...

PUA: Hey so whats up now?
HB: Want to come run with me?
PUA: I'm out of town but i'm planning on being back today sometime. Want to just hang out?
HB: I'll ask my mom when i get home.
HB: (some crap about her breaking up with her BF)
PUA: I'm sorry
HB: ok well ill call u in 15 min when I'm home.

I get a txt sometime in the next 20 min saying

HB: Mom said i cant hang out.
PUA: ok, well lets set up a day where u can.
HB: Hey i am getting in the shower in a little txt you later.
PUA: lol K.

Alot of my freinds have told me just to give up on her cause she has done this to me countless times and yet i still keep always pick up the opportunity to hang out with her even though i have other girls I'm sleeping with already. So could anyone tell me what i am doing wrong, or what i should do?

She just seems like she's messing you around, give a bit of silent SPAM to her, make her wait next time she calls and texts you. If she calls, say you'll call back and don't till the next day, same with a text, just say oh you had to go see someone, it'll get her guessing, then she'll probably want to hang out.

Alright i'll give it a try, thing is she has done this to me over and over again.
Normally she doesn't even dignify me with at least letting me know she cant hang out or w/e.
And in the event that she does agree to hang out, should i try to escalate anything sexually with her or just get her back into the comfort zone like when i was dating her?

Get back to the comfort zone, but also don't keep things too comfortable for to long or you will end up in the LJBF area, Kini with her after a while, DHV yourself, let her know what she has been missing out on.

she sounds like she has dependancy issues and is trying to contact you because she needs a rebound

Yea i thought she was looking for a rebound 2, but if thats what she was looking for then y the need to be difficult.
But I've thought about it a little and decided that screw her unless she makes plans with me day of lol...