Is it normal that i'm frustrated with my best friend?

I am joined-at-the-hip best friends with this girl at my Catholic all-girls high school. Let's call her Amanda. Since we met freshman year, we've gotten progressively closer as friends. We now are seniors in high school, and do EVERYTHING together.

And now I'm starting to hate her.

Here's a list of reasons why.

1)Amanda is a mooch. Her family is incredibly wealthy, yet she never brings money when we go out to eat. Meanwhile, my family is average, but I work two jobs outside of school and therefore have money on me. Amanda likes to do things on my buck. She "pays me back" when her family pays for me when we are all out to dinner together, and doesn't tell her parents that this dinner is indeed "payback" for what she owes.

2)Amanda needs attention. When Amanda and I are hanging out with people, she constantly interrupts me. Also, when guys have chosen me over her in the past, she feels the need to blab on about what strange anomaly caused him to choose me, and why he wasn't her type anyway. Also, according to my other friend Isabel, once when I was hooking up with a guy and somewhat MIA Amanda said "I just want to go hook up with him in front of her to prove that she's not that special." However, Isabel is a bit of a gossip/might have been lying.

3)Amanda is needy. Sometimes she steers me away from other friends, often grabbing my arm, or bringing up some inside joke. She's clingy. Amanda will call me at night with homework questions, and also will make plans to have me help her with homework. She gets offended when I tell her I have my own work to do, even though I am taking a much more rigorous courseload than her.

4) Amanda is selfish. We are staying together this summer. I already have one job, and she has applied to a cashier job that she'll hear back from soon. The other day I discovered a site that posted babysitting jobs. When she was at my house, I started applying to jobs on the site, thinking a second job would be great to help pay for college. One job I applied to was incredibly convenient location-wise and very high pay. After I applied, she got angry at me. She said that she had started to say stop when I was applying, and that I didn't listen to her. Amanda thought I should wait to apply to that ideal job until after she had heard from her job. If she didn't get the cashier job, I should have let her have the closeby nanny job, as she doesn't know if she'll have her license yet for the summer, because she hasn't booked her driving test yet. That was just too much for me.

Maybe I'm crazy, but this girl is really starting to get on my nerves.
However, this whoel summer I'm going to be staying with her at her father's beach house. I'm really looking forward to summer, and Amanda can be fun/nice. How can I deal with living with this girl? I confirmed a long time ago that I'm staying for the summer, and now it is too late to make other plans.

Also, am I normal for feeling this way?