If the girl is married -beware of commiting dhulm, if she's not - then openly and humanly tell your wife your feelings honestly so that it doesn't go out of control, then she'll trust you, and either assist you in bringing her home lawfully-if she'll come -or assist you in avoiding her.
It's happened to me twice in the past in Islamic settings - the purity and Islamic zeal is an indescribable attraction that isn't found in animalistic settings so i wouldn't say that your situation is bad just because it's a pure setting.
Now that i'm out of contact with them both and yet almost two thirds through my divorce iddah with nothing i know of in the pipeline - i sometimes wonder why i didn't take the opportunity when it was easy - but hopefully your wife is decent - and Allah swt knows best.
I was totally frank when confronted both times though - she was willing to accept when she saw my nonchalance but the others wouldn't, so i just blundered on for another 6-7 years of God knows what.