When To Cut Back?

Currently having a dilemma. I work for my main employer at .6 FTE which is 2 12 hour shifts per week. I also may start working with a new hospital at a .9 FTE which is 3 12 hour shifts per week. This is a lot for me, and I know I will not be able to continue it if I am accepted into nursing school. I have applied for fall acceptance.

This potential new second job, which I have an interview with the Assistant NM tomorrow, told me they are specifically only looking for a full-time position for night shift. Now when I filled out my application, I specifically put that I wanted to work part-time, though the position that I applied for was a full-time opening. I thought if she didn't want a part-time employee then she wouldn't call me. Well she did, three months after I had applied back in March of this year. I believe this hospital went on a hiring freeze, and I have been declined for all other applications besides this one. She would like me to come in for an interview tomorrow at 1 and I am debating on calling to cancel due to the fact that I just cannot work that status past the fall. It was not my intention on misleading this NM or anyone else in HR, but I really am at odds on whether or not to continue with the next step of the interview process.

My next thought was - what could a walk around the unit and an interview do if I decided NOT to take the position? It would be good practice, it is SUPER close to my home (about a block!) and I could give full-time status one final consideration and maybe a shot to give her a chance to get to know my personality and see if she could make this full-time position a part-time one. But there was this one other thing that bothered me...

When I received her voicemail I called the following next day during the afternoon around 2pm. She put me on speaker phone with the DON for that unit and directly asked her about my dilemma - to which she replied promptly a big fat NO. Not only was I somewhat insulted that my first conversation EVER being with her was on a speaker call, but she did not do a phone interview with me AT ALL. NO tell me about yourself? What is it that drew you to this position? Would you like to know anything before our interview tomorrow? She was also talking to other people (I assume the DON and whomever else!) in the background and I could hear her! Now I know I am in the wrong here with my situation, but the least you could do is honor my five minute phone call with a bit more organization and professionalism. It actually made me mad and bothered me after our call ended. She also asked me this, "You know how to get to HR right?" Naturally to which I replied, "No, I have never been an employee before, where is it?"

Despite that slippery slope of nonsense which made me leary of even accepting her interview invite I am now back to my original mishap. Now my common sense tells me that if the DON said no, then that is what the answer is staying. No charm, interview, or walk through will change that. Should I cut my losses and start over? I know I probably should have stopped her on the phone when she invited me to interview, but I was still pawing over the thought of possibly working full-time just for the summer (my own selfish desire) and if I need to call back it will be first thing in the morning if I decide to not go.

I have definitely learned my lesson: Do not apply for the position unless it is exactly what you can do! So any advice?