Hi Dizzy,
Deprivation of Capital happens when the DWP believe that a claimant has spent, disposed of or refused money in order to gain benefits. Spending in order to buy the house in which you live is usually considered acceptable but,as you have heard, the rules are not terribly clear and each Decision Maker can interpret them differently.
From what you have explained, I don't think your daughter will have a problem but you are right to get a solicitor to look at your plans. If you are going to do this, make sure you use one who understands benefits law, don't take the word of anyone else!
Nothing on this board constitutes legal advice - always consult a professional about specific problems