Am I coming off too strong with this girl?

It seems as though you've definitely grown on her. If she's spending that much time with you voluntarily and is kind of upset when you leave you're doing everything right. You could even stand to ebb it off a bit to get her to like you even more because you're of higher value than her. I say continue what you're doing or turn it off slightly which is hard because you obviously like her if you're willing to write this much about her. And all of it well paragraphed. You'll be fine with this girl if you don't speed things up too quickly :)