Many thanks to everyone for your input, all very much appreciated.
I have today sent to GRO London for a copy of the birth for a Kathleen
McKay born 1899 (as suggested by shaunJ), i think this is a good
possibility this is Lisa's daughter. Although in the 1901 census it states
she was born in Scotland, i think this may have been a white lie for
whatever reason. I could not find a birth in GRO Scotland that would
fit, so here's hoping its the London one, If i can confirm this is Lisa's
daughter then i would presume that either Lisa was using this surname
although not married to the gent or she was married a few years before
the marriage notice in the Boston Sun, so why the notice in 1903??.
That's if the surname really existed, i am beginning to wonder.
In the meantime i will try and find a marriage in the other Londons of the world.
I will keep you posted. Roe.