If she did move to Switzerland then she would have had to register with the local authorities. These registers are held at Canton archives, So I suggest you write/email Geneva Archives
https://ge.ch/archives/# (email address on the right). They will undoubtedly deal with an enquiry in English.
Her time with the League of Nations will of course be as a diplomat, then if she did return, it would be as an ordinary person. I say this as there might be different registration systems. They will know.
If nothing there, then start widening your search to Canton Vaud next door. However Geneva is almost surrounded by France, but let’s not get ahead of ourselves!