However, the phrase "Mary Taylor was all in for him" is a more common idiom and would mean that Mary Taylor was completely committed to the relationship with him.
Here's how you could break it down:
* All in: Means completely invested, with no reservations or holding back.
* For him: Indicates that the commitment is specifically directed towards the person in question.
So, "Mary Taylor was all in for him" means that she was fully dedicated to their relationship and willing to give everything she had.
Let me know if you have any other idioms you'd like to understand!