Do you know Chieko's surname and where she was from?
My Japanese mother is from the same era as your daughter-in-law's maternal grandmother. I did actually find some good information via Ancestry.com when I found the ship manifest from her journey here in 1952. I would start by searching for Chieko Weir and see what turns up on Ancestry.
If you know her surname and where she was from, it might be a little easier to find information about Chieko. Is your daughter-in-law's half-Japanese parent still living? They might be a good source of information.