I am sorry your family is going through this.
I do not think a caregiver would be the most helpful thing for your mother right now.
If your aunt (moms sister) is in hospice care, hospice will pay for grief counseling including group thearpy that includes other individuals experiencing similar loses during your aunts illness and for up to 12 months after death.
I think she would benefit from this type of support. You can ask your aunts hospice nurse about this.
If your aunt is not in hospice care, there are still very good support groups for the loved ones of cancer victems, specifically this refers to grief counseling and grief support groups.
A little bit of Xanax, unfortunatly is woefully inadequate for treatment of symptoms that are as disruptive and disabling as the ones you describe.
Panic is usually part of depression. Somewhat like thirst is a symptom of dehydration, sucking candy may make you feel temporarly better but it does not address the underlying problem.
Your mom may benefit from an antidepressant when the depression is treated the anxiety kn many cases resolves itself. She could also take Xanax as needed, but the underlying depression needs to be addressed and treated.
It may take trying more than one anti-depressant before the best one is found. And It can take as much as 6 weeks to start feeling better, but usually it is sooner.
Although I am sure everyone will want to avoid my next suggestion, it is possible the fastest way to stabilize your mother would be admission as an inpatient to a unit that treats mental illness.
The reason for this is she would recieve 24/ 7 treatment and observation. Should she have an adverse reaction to the medication or not respond to thearpy as expected this would be detected immediately and interventions and adjustments made by professionals who do this for a living.
She would also be able to recieve intensive thearpy which would teach her new coping skills which she is definatly going to need to deal with this very difficult situation. Your aunt is not going to get better, and neither is your mother unless she gets some intense serious help now, that help should include a professional psychiatric evaluation, and most likely anti-depressant medication, one on one counseling, group thearpy with other grief victims, support from her friends and family, clergy. A care giver would not be able to provide the support she needs.
Just a week as an inpatient could be all she needs. Then if necessary she could follow/up with a day program and continue to use the professionals as rescources.This would take the burden off your family and allow them to be their for your mother again. The reason they are avoiding her is because her needs are so overwhelming and cannot be met by them.Involving professional support, will effectively address her illness then your mother will not be frantically "emotionally hemorrhaging" on any and everyone. Its like trying to be sympathetic to a loved one who is having a heart attack, sympathy won't cure the disease, they need to go to the hospital and then with proper treatment the family takes its place in the patients life again, not as Cardioligists but as family members being there for each other.
It is very sad that she is going to the emergency room frequently for the panic attacks. That is the proof that her illness is being undertreated, improperly treated and some new solutions need to be discovered. This is no light matter.
Cancer is a killer, but it cannot take away a families love for each other, your mothers inability to cope is not her or your families fault. But it is doing damage that may not be easily repaired.
Start by going with her to her medical provider and discuss her response to the treatment so far.
God Bless and good luck
Also, its possiple that if your mother realizes that her frequent 911 calls and unreasonable demands of family members will be treated as her needing to be admitted to a mental health facility instead of the gratification of recieving more family attention she might make more of an effort to be a source of strenght and comfort to her sister and family.
If she is being manipulative, and I am not saying that is the case, but if she realizes that her family is going to set limits on her demands for their time and attention ,she may decide it is to her advantage to seek help from professionals and try to establish an inner core of strength instead of being more sick and demanding more attention than her terminally ill sister
Build in a motivator, if she can stay out of the ER reward her in some small way. If she cannot then tell her the family feels her needs require professional support, meaning psychiatric admission.