Her Mother Agnes died in 1934, and her Father provided for 5 years, which would take the date to 1939, when nothing more was heard of him. This of course was when WW2 broke out, which might be a route to check out.
I have tried to attach copies of David's birth record, and also his marriage record, but it seems they are too big for Rootschat's system, so if you want to PM me with your email address to have a copy, I will happily have another go at attaching them for you.
Regards,