After you mentioned the good qualities of another female, and desire to have a female like such.
The word 'catch' is used figuratively. It implicitly compares the person to a (good) fish that one has caught. A related use: He | she is 'a keeper', that is, not a fish that one would toss back into the water. A fish worth keeping.
When words are used figuratively, over time the underlying meaning is often forgotten, so that a person who uses these words might not be aware of the basis for the figurative meaning.
She is just saying that, from your description, the girl sounds like a perfect find, for dating or marrying.
catch - (noun) one worth catching especially as a spouse. Merriam-Webster