What Davu said :)
The verb "dar" can be roughly understood as "to result in" in many cases:
- Não vai dar problema? = Isn't it going to (bring/retult in) problems?
- Quanto deu a conta? = What was the result of the calculation? (The calculation resulted in how much/many?)
- Ela daria uma boa namorada = She would (be/result in) a good girlfriend.
Would I run into any trouble interpreting it this way?:
lend oneself or itself to something
Fig. [for someone or something] to be adaptable to something; [for someone or something] to be useful for something.
e.g. This room doesn't lend itself to bright colors. John doesn't lend himself to casual conversation. I don't think that this gown lends itself to outdoor occasions.
This is quite a submissive statement (which works for any gender role whatsoever).
I tried a literal translation to English: "S-/he would give herself up to be a good girlfriend."
I can't help but notion these occasional bipolar statements in the Br-Portuguese language (like any other language I've studied - occasionally). There's something very particular when you would be "good" at something while giving up "another something good" to reach this state of being/mind. It seems we're still not sure whether we should specialize or diversify our social relationships. I do think we're currently not (yet) in a state of mind where we're able to grasp some sort of balance between these two attitudes (or maybe on an emotional level we might do already). In any way, I don't think mystifying social practices helps us in both ways. I think we need a little less of frequent judgment (good or bad!) and a little more timespace where people can traverse from the trodden path and collect new-individual experiences which in turn can help other people in traversing their own narcissist judgments.
PS. This is a personal statement, I do not represent any -ism in any way.
To me it looks like just an idiom. You could make up a similar statement about the English equivalent "to make a good girlfriend": Why would she have to make anything? Is she creating something she is not, for the sake of pleasing somebody? It is fake? Can't she just be herself? -- which would likewise ignore the broader meaning of "make" as "achieve"/"result in" rather than "fabricate".