I hold my daughters mortgage can I assign that to my wife?

You can change title at anytime. If you are talking about the loan, she would have to refinance and qualify for a new loan that would pay off the old one.

Correct, you can change the vesting on title but to change the loan, it would need refinanced.

Not sure what you mean by "hold your daughters mortgage?" You have a contract for deed with her? You have a regular mortgage on the house in your name? You can add or subtract people for the legal title (ownership) of a home anytime very easily with a Quit Claim Deed. This would not change any mortgage loan. To change a mortgage loan, the loan would have to be refinanced.