That doesn't mean that nobody she worked with knew she had a grandson or that she never talked with anybody about her grandchild.
She was a vice president at the bank by the time she finished. I'm sure there were plenty of people working at the bank who knew nothing about her relationship to Obama. They might not have known anything about her at all.
That doesn't mean that nobody knew anything about her family or private life.
Your evidence reveals a normal situation in which co-workers don't know everything about each others' lives. It doesn't support the idea that she never talked with anybody about a grandchild because she was ashamed of him.
Back in 2011, there were several articles that covered this territory. One of them mentioned that none of the co-workers knew he had a grandson. She had no pictures on her desk in the manner a grandmother normally would. What I have posted is the ghost of just one article which did exist at the time.
Most of those other articles are gone, either succumbing to the dead link disease, or deliberately scrubbed.