What happened to teamwork?

Sigh....the other night at work I had a slight confrontation with an aide. This particular one has been a problem since she was first hired over a year ago....she has always volunteered to work and then the next day she is scheduled she calls in. Well...we have been having some issues on my shift for the past 3 mos mainly with the aides not wanting to help each other or work as a team. I think of them as a strong chain...with one majorly defective link...this aide! She signed up to work a shift this w/end and the night before she crossed her name out which no aide can do...only the nurses can mess with the assignments and the DON has to approve any scheduling changes. Ok...I asked her if she did it...she said that she got permission from the MDS Coord. a few days ago..which was a complete lie because I talked to that nurse myself. She didnt even know what I was talking about, bUt she confirmed that she didnt approve anything for anybody as that is the DON's job. Ok..well....she got smart w/ me and said she wasnt coming etc etc..so I kindly told her not to volunteer to work any more shifts since she cant keep her word and those girls were left extremely short..took me over an hour of MY time to find someone to finally come in and help them out. Anyhow..I called the DON to see what she wanted me to do..I was going to write this aide up...again for the 6 th time. She told me to count it as a call in and she would write her up herself (highly doubt that will happen). I also told her how she lied yet again about another nurse giving her the ok on this....this aide is older and thinks that we should all just do what she wants ....shes not even that old! early 60's and healthy other than being a trouble maker shes ok. The aide said to me "you'll understand how it is when you get older" and I said..."You knew how old you were when you applied and took your job here..you signed on the dotted line that you are capable of doing your job...regardless of age....no one discriminated against you because of that..you were hired on the facts you provided that you are able to work. If you cant do it...find another job. '...i think that this is how shes kept her job as long as she has anyways. She gets people to feel sorry for her. Im done playing games with her. How do you guys handle aides that completely lose their teamwork abilities? How does this get restored? Ive talked to them and talked to them about this and most are in agreement that the teamwork needs to be fixed. The question is....How?