Jacqui, To go throught the complaints process can take forever, I know was health service myself.
Sorry to be realistic, but time is very important regarding this.
Make an appointment with her G.P. and make one final personal attempt to sort it wit him. Failing that ask his reasons and demand he puts them on paper. That will put the wind up him.
If that fails go see her social worker, there has to be one attached to the home. Get him or her to support your case.
Then go and seek legal advice. Your lawyer can and will request his reasons and seek another G.P. to assess the case.

I would not advise to go down the road of the G.M.C. As once you do this,everything at your end will stop as this is now a pending case under review. If she has been in hospital for any reason of late, get your solictor to request a report from the doctor who saw her.

Good luck with it.