Mrs. Wälse is not named. Fricka refers to the mother of Siegmund and
Sieglinde as a she-wolf: "jetzt dem Wurfe der Wölfin wirfst du zu Füssen
dein Weib?" (W-2-ii). 

Here Wagner is mixing his main Siegmund source, the Volsungasaga, with the
story of the Wölfings. (Siegmund to Hunding: "Ein Wölfing kündet dir das,
den als Wölfing mancher wohl kennt", W-1-ii).  The main sources for
this clan were the Saga of Dietrich von Bern (Thidhrekssaga af Bern) and
the Hugdietrich-Wolfdietrich poems. 

Returning to 'Volsungasaga', however, we read that Sigmund and his sister
were twins, among the children (ten boys, of whom Sigmund was the eldest,
and one daughter, Signy) of Volsung and his wife, Hljód.  Interestingly,
Hjlód was not a "mortal woman", but the daughter of Hrimnir the giant. It
is possible that Hjlód was the daughter of Hrimnir who was described as
one of Odin's wishmaidens, earlier in the saga.  Volsung is the third of
his line, his grandfather Sigi being "reportedly" the son of Odin. So both
Sigmund's mother and father had connections with Odin. 

But that's all in one of Wagner's sources for the 'Ring', not in the
'Ring' poems themselves. Strictly speaking, Mrs. Wälse does not have a
name. If you want to give her a name, then Hljód (huh-l-yöd) is as good as
any. This Old Norse name translates as "howling", which seems singularly
appropriate for a she-wolf!