As an INTP female, she may be waiting for you to start something first. I am very shy, and honestly, I would never make the first move. I’m not so great at dropping hints either. She may be similar. The fact that she is very comfortable around you and even told you that she feels like you understand her is a good sign. Connection is key. Also when you said that your text conversations aren’t like they used to be, but you get along fine in person, then you have nothing to worry about. The people I get along with the most I barely text at all (just my experience though). But honestly, if you’ve known each other for that long and you have great chemistry, go for it. There’s a chance she may feel the same way. Good luck :)