Is it permissible for women to go to a walimah if there are separate facilities?

Answer

No, it is not permissible. It is not permissible to a greater degree than the impermissibility for women to go to the Musjid even if there are some type of hallucinated 'separate facilities'. 'Separate facilities' at Musjids and Walimahs are ploys of Iblees.