A question regarding team work..... need advice!

I work on a busy crazy hectic "general medicine" unit in a fairly large hospital.
on day shift things seem to go smoothly with the team of 1 RN and 1 RPN to 7 patients, the care is complex and usually at least one of the 7 is either trached or a fresh cva.
at anyrate, on night shift our nurse ratio drops to only 5 RN's , which seems okay sometimes but the issue of team work has been a major problem lately.

We have an RN who is very selfish, wants to just look after her patients, doesnt want to help with turns and changes n patient care of the patients who are not by assignment "hers" , for example, If I am on team one and she is on team 2 we have to alternate breaks , and cover for eachother, several times I have come back from my break and patients have been sayin they have been ignored , other patients have fallen out of bed and once even a patient pulled out his chest tube.

I doubt she does patient rounds and is scarce in the morning during rounds when you need help, once I was in with a patient having seizures and the call bell for another patient went off a whopping 45 times and still no response, after the patients seizures stopped I went to the front and this nurse was sitting five steps away from the call bell system charting!!!!!!!!!!!!!!!
I was infuriated, I have discussed this issue with the nurse personally, also with our hospital clinician and unit administrator, the behaviour is still continuing and its to the point where the other four of us on nights are scrambling because of her being so selfish
I really dont know what else I can do, the clinician even suggested that I talk to her one on one again as opposed to the clinician getting involved!!