Need some advise about MIL

So my husband and I bought a Mobile home together, and we are looking for land, but until we find some land, his dad offered to let us put it on his land next to his house. We were very great fil, but my husbands parents are split up. One time we told his mom we were thinking of moving in with his dad (didn't actually move in) she became hysterical. She cried for a few hours and said she'd never see us again, even though we told her we would still see her. She said she doesn't like seeing the house she used to live in. She's tried committing suicide a few times and has been admitted into hospitals at least once a month for the past 10 years. We need to tell her we are moving and my husband and I are both afraid of her reaction. We are moving the first week of June so we were going to tell her either tonight or tomorrow night. Any advice to make it easier on her so she doesn't admit herself in a hospital or try suicide again??