"Snorri lists 16 goddesses in the Gylfaginning without naming Sigyn. However, in the Nafnathulur (final section of the Skaldskaparmal), he lists 29 Asynjur, among them Sigyn.
Here are the ones named as Aesir Goddesses here but not in the original 16:
Gerðr (Frey’s wife),
Skaði (Njord’s wife),
Jörð (Thor’s mother),
Iðunn (Bragi’s wife),
Ilmr ("Sweet smell"),
Njörun (possibly a dream goddess),
Nanna (Baldr’s wife),
Rindr (Vali’s mother with Odin) ,
Sigyn (Loki’s wife),
Þrúðr (Thor’s daughter),
Rán (Aegir’s wife).
The list goes on with 11 more Valkyries "And these others are Óðin's maidens:" which includes Eir and three Norns: Skuld, Nift and Dísi." (thank you, Linda).
Now, I don't put much stock by quoting lore, but I've made an exception here. It's clear, as it has been for years, that all too many Heathens who claim to value lore and who look for it as a guide to their religious lives, pick and choose and value only that which makes them comfortable and demands no effort either ideologically, emotionally, and most of all spiritually. Pathetic.