Heather vs. Lisa: What happened?

I am current on all seasons and episodes and I cannot figure out what Heather’s deal is with Lisa.

PLEASE fill me in. It seems like more than anyone else, Heather WANTS to have conflict with Lisa…but why? Every single housewife on here is crazy in their own way but Heather really takes Lisa to task on everything, whereas she makes concessions for the others.

Is it because they’ve known each other for a long time? Did something happen off camera that hasn’t been stated on the show but maybe the blogs? I CLEARLY missed something.

Help me out, friends. Why does Heather seemingly hate/target Lisa?

And before anyone gets on it: No. Lisa is no one’s “victim” nor is anyone defending anyone. It’s a question.