She may have already come to that decision and has made peace with it.
Sometimes people who have struggled with depression, once they have made the decision to suicide, have a kind of transformation where they seem to be much happier, peaceful people - it's because they finally see an end to their pain and suffering.
The fact that she's sold her home and is looking for ways to spend the money that will benefit family members is a big red flag, imo.
The other thing would be to find out whether your mother has a plan for suicide and the means to carry out the plan. Does she have access to medication that, in combination with alcohol, would cause an OD or respiratory failure - something like sedatives, narcotics or antidepressants? Does she own a gun? Does she live in a highrise apartment with a balcony, or near a bridge, or near train or subway tracks? The major concern for me would be alcohol and pills - that is typically the method of choice of women - they don't want to leave a mess for others to have to clean up.
While JWs used to consider suicide as an unforgivable sin - unworthy of Resurrection™ - the current belief is that it is not possible to know the mental state of a person who is suicidal, and that their eligibility for Resurrection™ is in Jehovah's hands.
My suggestion to you would be to get in touch with her doctor, ASAP, and while the doctor may not be able to discuss your mother's medical information with you, you can inform her of your concerns and the doctor can assess your mother's status and refer her to a mental health professional if she feels that there is significant risk. That is, assuming that your mother will be seeing her doctor prior to your visit, to intervene sooner rather than later.