Aware of the past posts and problems, like Annie and Carole, trying to help you move forward now...
If you don't have these documents already, you need to get Isabella's birth, marriage or death cert to help you move on backward with hard verified details to work from. Can't begin to tell you the number of times people start with guesses...and just stay there without being able to confirm. 20th Century records can be so hard to confirm because you start to hit all the restrictions due to privacy/data protection (understandably really). Pick your certs to order and view, until you get back enough so we can all help with online resources.
Working online, for your info, SP have the following restrictions to viewing online images (as opposed to having to order them, or view them at a main Scottish genealogy centre or Registrar's Office):
Births - 100 years
Marriage - 75 years
Deaths - 50 years
Monica
