When you call HR to follow-up (again) on your application, let it be known that you are willing to work just about any schedule -- full-time, part-time, per diem, etc. Nights if you can stand working nights. Tell them you love working weekends and holidays.
Make yourself look about as flexible as can be. Also, if you met any nurse managers (best bet) or even staff nurses while you were doing clinicals, don't be shy about contacting them to give your application a boost. One call from a nurse manager goes a long way in many hospital HR departments.
I would not give up yet. I know you need to work, so take any job you can get at this point. But keep trying. Come June when they realize their vacation schedule has created headaches for them, your application might start looking a lot better. Persistence really is the key.
One other thought: contact your local home health agencies. I have seen ads from these agencies for 2nd year nursing students to act as CNAs, aides and/or companions to homebound folks. That would pump up your resume for sure.
Good luck, and keep your chin up!