im amazed... why on earth would you pay for private medical insurance for her? i cannot undertsand how she has come to the conclusion that that is an acceptable or even logical thing to suggest...!
and to start demanding refurbishments!
i think you need to take her aside and tell her straight it is YOUR house, and under no circumstances will it ever be hers, so to get that idea out of her head.
and also state that if it ever did, you would take your entire investment out of it, which she would have to pay.
i would also suggest to your dad that the £85000 you put into the property now actually makes you majority shareholder in whatever percentage that amount is of the whole property, and would he mind agreeing to that on the deeds ... say it is just to keep your own books and accounts in order etc, and dont let her know what you are doing...