The au pair needs to apply for (and obtain) another form of lawful status, or return home.
I'm not sure what you mean by having her J-1 visa transferred. If the au pair is seeking an extension, category change, or program transfer for a J-1 visa, such matters are handled by the The Program Designation Branch in the Bureau of Education, Cultural Exchanges and Academic Programs (ECA). She contact them directly at 202-401-9810.

