Confront or Turn the Other Cheek?

When another Christian hurts you personally, how do you know when to confront (according to Matthew 18:15) or just turn the other cheek?

I am absolutely lousy at confrontation when my feelings have been hurt. When someone else is wronged, I don't have as much of a problem speaking up. But when someone does or says something hurtful to me, my tendency is to turn the other cheek.

My question is this: is there a point where turning the other cheek is the wrong thing to do? Where's the line? How do you confront someone in your own family, outside of the church?

There is a person in my real life who has been hurting me repeatedly. The latest episode was this past weekend. Out of nowhere she dragged out my past and began recounting all the wing-nut things I did when I was in the old church. She told me and everyone present that back when I was in my old church, I was driving another family member crazy all that time. (Funny, he never saw fit to tell me that himself, why bring it up now?) I burst into tears and said that I wanted to stop talking about it, that these things were very embarrassing, but she kept going.

I feel like I have to repent all over again. And I'm a little depressed to hear that I was driving this other family member crazy. That one really, really hurt. Two and a half years later and I'm still paying for everything that I thought was in the past and forgiven.

The problem is, it isn't the first time this person has started in on me and then refused to stop when I was clearly distraught. It's been happening for a long time now. It used to happen on the phone. She'd harangue at me for over an hour. One night it got so bad I just hung up on her, then felt incredibly guilty and sinful for doing so.

Conversations with this person often start off benign, so I let my guard down. Then out of no where, whammo! She blindsides me with something I never saw coming. It's like riding in a car with no brakes. Once things go off the road, you expect that both parties will stop, apologize or talk things through, and then change the subject. Not so with this one. Things just keep hurtling along, getting more and more out of control until I crack or attempt to remove myself from the conversation by hanging up or leaving.

In the past, I've just tried to get out of the conversation however possible - sometimes I take the blame and just agree with her. Then I listen to her go on for ten or fifteen minutes more about why her viewpoint is correct, while I wait desperately for an opportunity to change the subject. Sometimes I try to defend myself, but I found this only fans the flames and she becomes even more strident and determined to shoot down everything I say. Lately I've just been trying to avoid talking to her, but she's family and that only works for so long before she corners me about not talking to her and starts grilling me: "what's wrong? What's going on? etc."

What do you do in a situation like this, when you know the same thing just keeps happening over and over, but you feel powerless to change it?

Yesterday she sent me an email saying that she felt bad about upsetting me, which is as close to an actual sincere apology that I am going to get. I finally replied this morning, and decided to tell her that she hurt my feelings and embarrassed me, that I was frustrated, and I didn't know what was a safe topic of conversation anymore.

I stared at this email for almost an hour before sending it, a knot in my throat the size of Texas. But I did send it. Now I am dreading the response.

I should have just let it go. I shouldn't have said anything.

I am so bad at this.