Can my mum do this to me legaly?

I think you need legal advice from a lawyer, but I will give my two cents. I personally would try to get that money by any means possible. Unfortunately, you verbally authorized the placement of money in her account, therefore to my knowledge that's like giving it to her. So, depending on the legal stuff set forward by the trust, that money might now be hers. Still, there's a possibility you can get it back. Like I said, talk to a lawyer/attorney.