Dude, vengeance of the type you speak of is unwell.
Talk to her about it.
Maybe even consider romancing her a bit and explaining things. Talk it over. Take her on a retreat or rent a cabin and make her cum a lot.
Don't use her family or her past (that she TRUSTS you with) to hurt her.
You guys need counseling, but not of the type that involves an outsider. Look to heal things by communicating and expressing yourselves much more effectively.
Be a lord, and have her be your lady. Apply yourselves, and maybe you can find some way to mend this rift.