I'm questioning my friendship with her

I've been friends with this girl since I was in high school, we've always had a great friendship but I had to cut her off because at the age of 21, she expected me to pick her up and drop her off *every time* we hung out (she lives an hour from me). Even worse, she expected that I pay for her meals & drinks!
Eventually, I couldn't bare the financial strain of spending over $500.00 a month just to hang out with her. We somehow managed to get back into contact several years later. Hoping that she had been able to get onto her feet, I started inviting her back into my life as my friend.
Now that we're hanging out again, we have so much fun with each other, we travel, we lift and run together, go hiking and clubbing; but I'm starting to notice her mooching *again* (even though she earns well over what I do). She's expecting me to pay for meals, drinks and expects to have a free room and board at my house with meals included 3-4 times out of the week.
I'm only 2 weeks into the month and have already spent $400 just going out with this girl!! I'm falling behind on school now which is causing me to miss work (because she is constantly coming over uninvited). This month, in addition to having spent $400 on "fun" I will be taking a $300 cut because I've had to miss work to catch up on school. When I tell her I can't hang out, she proceeds to act in a way which makes me feel guilty and selfish.
I'm not a lonely person, I have a lot of friends and feel like I shouldn't deal with this but feel bad about cutting her out of my life.
Is it time to cut this girl off again?