Along with convincing yourself that she's a projection of your mind, next time you see her, tell her you enjoy her company, and that it's alright if she doesn't appear as often. If she's as sentient as you claim, she'll understand your situation perfectly.

She's not appearing in your dreams as often for a reason, just like she appeared for a reason. It's not up to me to figure out that reason (my conjecture is that it deals with social maturity. Perhaps, on the inside, you want your shyness to melt away, and have the ability to handle yourself better socially. Being dependent on the girl hinders it, so she disappears.).