You need to come across and let her know "Hey thats not cool to be doing that in my presence, not allowed". But of course you cant use those words.
Ask em whats up with the texting? Various ways of doing this. Ask em Hey are you a drug dealer? Who are you texting your mom/dad?(should make her smirk)...figure out a few good lines for yourself to use . Why sit there and adhere to some BS like that if its disabling you from getting to her.
If in fact your trying to game her and she realizes it shes going to be texting or on her phone alot, trying to seem like everyone and anyone wants to talk to her and possibly to see how you handle the situation of her trying to blow you off. And I can guarantee some times the chick is infact texting about you in your presence(YES) to one of her GF's...cause how else could it possibly add up that every time shes in your presence that her phone is getting blown up to bits?
A real smart chick was running this routine on me, and I said hey whats up with all the phone activity are you a drug dealer....short pause and a smirk on her face as shes continuing to text...responds to me Yea i am actually what do you need(this coming from a girl that obviously does not deal). I sit looking at her puzzled

and she says NO NO im just kidding im not really one. Then after that she never had it out again during that instance. Only reason I knew it was a front cause "to look" occupied i do the same shit when there's idle in between moments. Plus checking your phone twice in 30 seconds, without any notification that you received a message or anything sort of draws attention that your wanting people to think your important.
You could also run the, hey is that the **** *** phone...can i check it out? If your on a high note making it good with the chick this would be a good time to input your # and save it(if you can manage)...dont say you did it though. Just a cheap example as im sure in the moment you could figure out some other clever way to make a number exchange out of the ordeal. I'd say as well too if shes not obviously doing anything but just playing with it that could be a hint that she has it out hoping to grab your digits(if you do not have them already).