As there are no options, there are two possible answers.
If Teresa's daughter is my daughter's mother, you could be Teresa's daughter or Teresa's son-in-law.
In the riddle, three generations are mentioned: Teresa's, Teresa's daughter's, and Teresa's duaghter's daughter's. Imagine a family tree:
<h3>Teresa</h3><h3>↓</h3><h3>Teresa's daughter ↔ Teresa's son-in-law</h3><h3>↓</h3><h3>Teresa's daughter's daughter.</h3>
As it refers to a daughter's mother, you can rule out Teresa's daughter's daughter because it was not said whether she is a mother or nor. And as it also says Teresa's daughter, you can rule out Teresa because Teresa can't be her own daughter. So it can either be Teresa's daughter or Teresa's son-in-law.
