There are many city directories for Boston in the 1940's right on Ancestry. I would recommend that you look for your mother in there. Who knows maybe they even shared a household (lived together) (aka boarder...) 1947 and 1948 specifically are there.
If they aren't listed together you will need to go to the Charles Smith's and look for the likely ones. If you list them out and then google the addresses you might find someone very close by.