Groups. Game the whole group. Aim to win the whole group over. You can ask the group about the person you're most interested. EG "Is she always this sassy?"
The group advice applies for when she's with her mum. Game the mum. Get the mum to talk about her daughter.
On her phone or headphones. Indicate with your hands that she should put them away. Then start speaking to her if she does. If she doesn't roll your eyes, shrug your shoulders, sigh to yourself. If she still doesn't respond to you, carry on with your day.
Stop taking all this so seriously. Lighten up. Have fun. Enjoy yourself regardless of the reaction you get and the impression you make.