http://www.bloomberg.com/apps/news?pid=washingtonstory&sid=ahv9BUQLp6SI
This is what it originally said: (From Bank of Hawaii Co-Worker Jackie Berry.)
Berry said she didn’t realize Obama was Dunham’s grandson until early this year while watching TV.“She was pretty conservative from my point of view so back then it would have been surprising” to know she had a black grandson, Berry said. “I would have thought: `I wonder what she thinks about that?”’
And lest you think I am making this up, I will point out that another person found this exact same article. (Look in the Comments posted June 4, 2011 at 11:54 am) Their supplied link is also now defunct, but that is what it said back when it worked.
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.