iPhone is blocking contacts as well as Facebook messenger contacts.

I’ve been dealing with this for a year now. It’s gotten to the point where every day I have to routinely unblock her in Facebook messenger and in my phone contacts. My Facebook isn’t hacked- I’m the only one accessing it. I’ve been trying to find a solution to this, but I haven’t come up with anything. Just recently, it’s deleted our entire Facebook message history while blocking her. Several weeks ago I was notified that I tried to report her Facebook account. But it isn’t just Facebook, or I would try contacting them for customer support. It also blocks this contact in my iPhone contacts. No one else has access to my phone. It’s absolutely crazy, and I don’t understand what’s going on. If anyone could offer some insight, or even who to contact besides the basic Apple customer service that would be so appreciated!