Another immigrant, another quagmire.
There have been a lot of unorganized merges.
The basic "source" is Ancestral File, but AF only calls her Mrs Thomas East. Which implies that she may be only an inference, not mentioned in any record at all.
Somebody might have misinterpreted the Thomas as her maiden name. It happens.
There's a child born 10 years before the marriage, so nothing here smells like it actually came from a primary source.