Death Records Now

I’m trying to locate my great aunt -Margaret Dougherty – whom I knew nothing about until yesterday when I found a letter from a Mrs. Weston informing my great grandmother that she had died (1923) and was to be buried in the local church, the funeral was to be paid for out of the $300 she had in her bank account. With it I found a letter from margaret dated a year previous, begging her family to take her home so she could die in Ireland. I cannot seem to be able to access any online databases…i know she had been in a hospital

Where should I start?

You don’t say if Dougherty is your aunts birth name or married name.
I have done a search on ancestry.com and the only record I could find was a 1920 census listing a Margaret Dougherty aged 66,born in Ireland and living as a lodger at no.6 Bells Court,possibly flat or room 55. She was single and unemployed and unable to read or write.This was in enumeration district 122.Area5,Philadelphia,Pennsylvania. If this was her and she died in 1923 she would have been about 69/70 (1854–1923)
This seems to have been quite a large boarding house and there were quite a number of other Irish boarders there. If it was her,she may have got someone else to write a letter for her.
Cannot find a death record for her. Hope this helps.
edit: Just found some passenger lists but need a probable birth year to try to match up margaret as there are a number of people with the same name.