Dude, are you a masochist?
If you go into hero mode with an INFP female, you're basically writing your own death wish. Well, this applies to NF females in general, but especially with INFP females.
What will happen is this:
You will be smitten by her sweetness and vulnerability.
. . . . She falls hard in love with you, while constantly pointing out her flaws because of her vulnerability which you mentioned above.
As she starts to trust you, she will dump all her deep rooted emotional problems unto your bosom. Until one day, she will reflect on it, and start to feel a bit too vulnerable from baring herself so much to someone else. And perhaps even a bit ashamed at baring so much of herself to another person.
Then the resentment will slowly begin. In order to not feel so vulnerable/ashamed anymore, she will start to close up to you, until she eventually just dumps you, and walks away, leaving all her baggage behind in your heart. You will be left with all the emotional mess she had previously confided to you.
This mess is comparable to a broken vase, but even if you do repair the broken vase, there is no owner to return it to, because she's already moved on to give another broken vase to some other unfortunate bloke.
That my friend, is the story of the [NF] hero, and the INFP damsel in distress.