Hey guys. I'm having a dilemma here, so I want some advice from y'all.

Background:

Met a cute highschool girl(Girl A) through a trip. She's always with her sister(like always). I'm assuming it's the fact that she is nervous with new people. I saw them alone, so I approached and talked to them, to get to know them.

From what I noticed is that, eye contact is strong, but arms are always crossed(Girl A), and the girl is always clinging to her sister(Girl B)--like in a table of 3 chairs, she would move her chair toward her sister than letting the chairs be equally displaced--but not only that but they're both quiet af. It's really hard to keep a convo going with them because it just becomes boring from their lack of response. I can tell that they want to talk, but they just don't know how to follow it through. I'm assuming they're just nervous, or it could be that they're not interested in me. Normally in this situation, I just walk away and do my own stuff.

I always catch her, and her sister staring at me...so I'm not sure if this is a IOI.

Her sister is very receptive to me because she always stares at me, and I whenever I look, she's always the first one to look back(Girl B). She is always the one waving bye back and such (this was during the trip). I was able to apply some kino with her (Girl B) and it was receptive: just touching her hand and stuff to see some designed nails.

So my question is this:

I am going to be seeing them later this week. I am going to approach them and have a small talk, if they're being boring, should I just ignore them throughout the day? or is it up to me to carry the convo all the time?

and also, do you think I should just talk to girl B more than girl A due to the receptiveness I receive from her? I feel like with a little bit more time, I can make girl A more receptive to me(I catch her staring at me all the time), but idk if I am just wasting my time with that.