I have gone out with a girl a few times, and she is very flirty and friendly with me, but doesn’t say what she wants. I don’t know if she’s interested in me, if she wants to consider a relationship, or if she just wants to go on a few dates before she tells me something specific. I like her a lot, but I am also turned off by people who just don’t want to speak clearly and tell me what’s on their mind. I am tempted to ask her, but don’t want to come across as too pushy. What should I do? My friends say I should ignore her and wait until she gets back with a message, but that sounds like an immature thing to do.
Your friends are immature, and you’re right to ignore their suggestion. It’s okay for someone to take their time to communicate because you can’t expect everyone to operate the way you do. If you like her and want to meet her more often, that is all that matters, and is presumably why she agrees to meet you too. Give it time, allow her to get more comfortable around you, and ask a direct question when you feel as if you can have that conversation with her. Until then, why assume anything and let go of someone who may be great to have in your life?

Can physical attraction between two people develop over time? I have a close friend and have begun to have romantic feelings for her. I don’t know if this is just because we spend so much time together, or if it’s because there is something genuine between us. How will I be able to tell the difference?
You should do what you have always been doing, which is treating her as a friend and seeing how you feel over time. If you are close enough, and aware that this may be awkward, why not tell her what’s on your mind and allow her to process it?