Again, thank you to wonderful, friendly cemetery personnel who are willing to help family researchers like me!
The 1900 Census shows great-great grandma as widowed and having 2 children, of whom 2 were living. One was obviously her daughter. The other, I think, was a son who lived in another apartment in the same tenement house. In those days, small families were rare, so my conclusion is that she was widowed early and rather than be left behind when her 2 children moved to the US, she came along. That must have taken courage, IMHO, knowing that she might never see her other relatives and friends again.