OK, so she may defend it on the basis that it was a gift. However, the Court will look at the surrounding evidence. Ie her ability to obtain credit, whether she made any repayments (and if she did that is contrary to the fact that it is a gift). There is also a "resulting trust" argument - ie there is a presumption at law that when A advances funds for property in the name of B the property "reverts" to A.
I am not so convinced he has "weak legal grounds" - but then I haven't seen the evidence which is what these cases turn on. I would be inclined to suggest to your mate that he goes to see a solicitor WITH the evidence he has and gets his/her view.