Heya again

I don't think any of the truth you want to say to your stepmom will ever come over as nicely, simply because she will never want to hear anything negative about herself. Some folk see no blame in their actions (and she comes over as she doesn't because of your sister), and then it's pretty much impossible to have a good and fair conversation with them. (I've been there with my parents, my dad mainly).

So it kinda leaves you to either tell the truth, sugarcoated or not I am sure will have the same reaction from her), or suck it up and not tell her how you feel in order to keep the peace.

You mention that you HAVE to have a relationship with her - why? Is it so you keep seeing your dad? Just wondering if you can work something out with him if you really do not want a relationship with her again, nor to apologise?

Good luck... and sorry this is happening. It sucks.