If I am on a phone conversation and she will not let something that is unpleasant go I give her three very nice warnings and after the third I hang up the phone, or leave the room if in person. I am nice about it, but you have to be firm with her or else it never ends.
I agree with everyone above, and especially with BookGrl's comment about giving three chances.
Although I've never had to tell my parents I would be moving out of the country, I did have to tell them I was moving out of state at a relatively young age. While they were reasonable and told me "it's your life," I still received negative feedback until I moved back home a year later. Now, I get berated about my "failure" in the other state to build my own life, and reminded about how I had to "come crawling back."
But the point is, you do not have to take any of it. If they're going to throw guilt trips on you and pitch fits, then they're not being supportive. This needs to be made clear to them. Personally, I'd go about it this way:
Call your mother, ask her if you can come over for lunch or something.
When you get there, tell her that you need her to sit and listen until you're completely finished before she makes any comments. Make that
very clear, and if she interjects at all, hold up your hand and tell her to please wait until you're finished. If she continues to interrupt you, explain that you feel like she isn't respecting you and allowing you to fully explain, and let her know that you may be already about to answer her questions.
Explain that the move is already decided, and nothing she says or does will change that decision at this point. Explain that what your family really needs right now is her love and support, not her negativity.
And lastly, ask her if she has questions. If she asks snarky or meanspirited questions, calmly tell her that her negativity doesn't help you in any way, and feel free to tell her that she's being ridiculous when necessary. Defend yourself, but within reason.
It's really had to do this kind of thing, and everyone here probably has better advice than me, but I think you just have to be extremely firm, and very repeditive. Repeat a million times, if need be, that her negativity is not going to change your mind and only results in you not wanting to spend time with her. Tell her that you need support because it's not going to be easy, but it's already settled. Pound the message in.
![Smash [smiley=smash.gif]](https://www.talk.uk-yankee.com/Smileys/classic/smash.gif)
That's just my idea, and even though it sounded like to was trying to tell you what to do, I was just trying to give an example of what I would do to maybe give you some ideas.
It sounds like you may get a confrontation from her, but it still doesn't change the fact that you have to tell her :/
Good luck!!