Re: Complicated situation
What was her body language like the next day when you asked her out for coffee. Did it look like she wanted to make a quick get away, she was annoyed? If she’s extremely shy, which a lot of us desi women are around the opposite gender, she might be sending mixed signals. She really likes you but can’t get up the courage to say something. I don’t think her sister would say B does not have a problem with it, if B does not really like you. We really don’t know what B’s thinking so wait until after Ramadan is over.
She might be very conservative. You represent a non-mahram to her. Being alone with her in the pantry was by itself a bit haraam-ish.
Now that I think about it, take the route of talking with her father and brother first, if you are serious about her.