How to I cope with my depressed mother?

Oh Gosh......I am overwhelmed and would appreciate any advice u may have.I do have to provide some background ,i'll try to keep it short as possible.My mother lives alone and has severe rheumatoid arthritis.She is 81 yrs old.She does not have any form of dementia that we are aware of.She is severely depressed,she cries 24/7.My dad and her were married almost 55 yrs and he passed away a little over a year ago.He was her life ....she was financially ,emotionally,physically,socially dependent on him for many years .he did everything for her and she allowed it.He treated her like a princess...she could do no wrong in his eyes.She is a smoker...he wasn't.But he supported her smoking habit their entire marriage.His health failed (had a heart attack)...but had surgery and lived a pretty productive life..we(myself and 3 older brothers )woudl say "mom u shouldn't be smoking around dad"but she continued to smoke anyway.No one was going to tell her what to do .Her arthritis was getting worse and i set up an appointment to see a rheumatologist....took time off work and drove 2 hrs .the doctor was very promising and said they could help....but she would have to stop wearing high heeled shoes(she was always very vain and always had to "dressed" when she went out".Anyways ...set up a followup apt and she refused to go "no ones going to tell me I cant wear high heels".I was so frustrated...we informed her it was just going to get worse and is noe debilitating.Her GP has tried to prescribe meds over the years but she has refused to take a lot of it because " they have side effects"and she is "scared "to take them.I can't tell u the countless arguments I have had over this.....but she is so stubborn she will not budge .So I just don't argue anymore.Since dad died she is trying to put all her dependencies on to me .I am married and have 2 children...very busy .But I still go visit, take meals,buy groceries,smokes...still hasn"t quit,medications(antidepressants and pain killers etc.I do have 3 brothers (one brother has been a big help...we were sharing to errands and visits..but he recently moved 3 hrs away...he has a autistic son ...they moved to get better treatment options for him).My other 2 brothers r 10 minutes from her house and visit ..one brother...once a month maybe and the other ..3 months will go by ...doesn't even call.I have asked for help but they choose to bury their heads in the sand so to speak.Mom and I always hasd a pretty good relationship...but I admit her dependence on others and her expectations of others ...even my dad before he died has sufaced anger and resentment.When we have tried to help her.....she snobbishly says no....that won't help.She seems like she would rather have the pity.My patience is wearing very thin.especially when she says"i wish there was something out there that would help me" ...the doctors don't care".Grrrr!!!I recently took her for a hearing test because her hearing is really failing....they concluded she did indeed require a hearing aid...we left without ordering one .....not for financial reasons ....but because they r just trying to make a sale or rip her off.I said"mom u really do need it"....her response was WHAT????.....i rest my case.Like I said I am done arguing with her.She is also VERY afraid of dying....so when people ask "would she hurt herself" ........she is so afraid.....i know we don't have to worry about that.She is very lonely....she has no friends ..she has alienated herself from others.I am her only so called friend,I've read other posts who say to distract and i do try to do that.T.V. is her best friend,So we talk about different shows etc.The other night was the worst i have seen her in along time ,,,,she was sick...she says...weak.I asked alot of questions ..but I couldn't find anything physically wrong.She cried the entire 2 hrs I was there.I just don't know how to deal with that.What do I say?I don' have it in me to coddle her or pity her...I am angry because i think where she is in her life ..is all her own doing.I want to have compassion but i am losing that quickly.I cried on the drive home.Advice has been ....just walk away...u have to think of yourself too and your family.I always said I wouldn't let her do this to me like she did to my father.,emotionally is where I have trouble walking away.I was supposed to go color her hair this week and i'm finding it harder and harder to go.Also I should mention ...she does have a "lifeline" button she wears for emergencies.....she has used it once.I also have personal care workers coming in to do lighthousekeeping and meal prep once a week.They r also there to help her in and out of the shower but she won't let them......she 's too modest ,vain and proud.She won't even let me help her.so she just washes at the sink herself.Like I said I'm overwhelmed.I feel like I'm getting depressed and I don't want this to affect my family.
Sorry about the length,any advice would be greatly appreciated