Have checked for gravestones:
Isabella Bell - died 23 Nov 1901 - Ward 3 Row U No 283.
This grave is located in one of the older parts of the cemetery and has been left to nature. Section U appears to be for babies and young children and there are very few gravestones. There was no gravestone for Isabella. From the burial entry Isabella was 6moths old, which explains the plot site, and lived at Irvings Place, Rickergate. Several other babies were buried on the same day in the plots next to Isabella and strangely one was for a still birth of "Isabella Bell's child" of 47 Broad Street, Carlisle! (probably no relation - just a coincidence)
Isabella Bell - died 3 Aug 1908 - Ward 14 Row M No 90.
This grave is also located in an older part of the cemetery and again has been left to nature and has very few gravestones. There was no gravestone for this Isabella.. The burial record shows her as 36years old and living at Trinity Buildings.
(for info -There was a gravestone in Ward 3 for an Isabella Bell of Brunswick St, who died December 1917 aged 80.
There was a gravestone in Ward 14 for what looks like a William Bell died Oct?, his wife unreadable and a daughter whose name begins with M, the gravestone was very badly worn, but the address on it may have been 4? ? ? ? Street, just thinking about the still birth above - probably not your Bell's though as it is a fairly common surname just thought I would mention them incase)