Personal belongings and (ex) family

[momandme]

My mother bought a house in California. My brother, his wife, and their young son moved in with her. They paid some bills and helped with food and such. Shortly after moving in, they had some marital problems. She moved out leaving her belongings, saying she'll return in two weeks to get them. She did not. This was February of 2004. She returned to California in November of 2004 and retrieved some of her belongings, but left a note [my mother was out of town] saying she'd be back soon to pick up the rest. Here we are in April (almost May) of 2005 and she has still not returned to pick up the rest of her belongings.
My mother has repeatedly told my brother to tell her [which he did] that she'd have 30 days to pick up her things, otherwise she'd sell them. His wife would tell him that she'd pick them up soon, not to worry.
My mother is currently cleaning and repairing her house and property because she will be selling her house next month, and wants to get rid of the stuff that she doesn't want cluttering the house when it's shown, and is getting rid of items that she will not take with her when she moves. This includes my brother's wife's personal belongings. (They are beds and a washer and dryer and a few other items.)
Recently, my brother's wife told my younger brother that if my mother would keep the items another month, that she'd pay her for her troubles. [We find this hard to believe since she has been working and living with friends paying no bills and has yet to buy her son anything he needs when he stays with her]
Does my mother have to send a letter and give her a specific date to get her stuff out of her house? There was never any rental agreement or anything, it was just family living with family.
Can my mother be sued if she donates the items, even though it's been well over a year and my brother's wife has not taken them? Sending the items directly to my brother's wife would not be an option, since she is currently living in Arizona while the belongings are in my mother's house in California.