Sandy here are no winners in divorce. I do think that divorce sows seeds of doubt in all of us. It's not about siding so much, in my experience, but a lot about how you might be received by others in the family.
Writing about it I am sure helps, but I'm wondering about your niece. Is it possible to reach out and just ask how she is? She may just be on the horns of a dilemma, not knowing how she might be received by you.
And if you don't hear from her? Well you sent the olive branch. Not easy, but maybe an opportunity for healing...my penny's worth. :)