Welcome to the forum. When you get a chance, and assuming you wish to do so, please introduce yourself in the Introductions thread.
I am so sorry that you are going through such difficulties with your mother. I don't know the laws where you live or the circumstances surrounding your mother's threats, but I don't know if any court recognizes "grandparent's rights" to access to their grandchildren. Unless you have been brought up on charges of being an unfit parent, your mother may be throwing out hollow threats to you. However, I am neither an attorney nor an expert on such matters. I'm just offering that as an opinion.
As for work you could be doing, you should consider Hot Foot products to get her to stay away from your family. The spell kit is advised because it contains everything you need, plus full instructions, so you won't have to guess at anything.http://www.luckymojo.com/spell-hot-foot.html
I am also merging your post into the appropriate thread on getting rid of unwanted people. Please read through the thread and you may get other ideas on how to approach this situation.
I wish you the best of luck!