Sigfryd is a fake persona donned by Walther III The White Mongoose while travelling around Waterdeep with the Divine shanks.
Sigfryd is cheery and delightfull and wants to save her brother from the maws of the Undermountain!
She has a bow but is never seen to use it.
Her voice sounds nothing like Sigurd’s as Walther has no Idea what Sigurd actually sounds like and crafted this persona solely on superficial information he got from the Divine Shanks and the Zhentarim.