Julia is actually currently Madame Web (Who I BELIEVE is in a coma.). But she was Spider-Woman for a period, and she was a member of Mystique's Brotherhood of Evil Mutants, who operated under the title of Freedom Force at one point in the late 80s/early 90s. They weren't KNOWN to the world as the Brotherhood, or as criminals (I don't believe.), but was it ever explained why Julia was a member of the group? When did she find out about them being the Brotherhood? Julia is really "my" Spider-Woman. I read more comics with her as Spider-Woman, and I like her better than Jessica Drew. I don't really like her being Madame Web. She always had more of an edge character-wise than Jessica anyway. But maybe that's just me. Speaking of Jessica though:
#In the last issue of her original series (#50, I believe.), she had a big fight with her nemesis, the supremely powerful, magic-based Morgan Le Fay (Or is it Morgana?). She died. Or was she erased from existence? Obviously, she came back. When and how was it explained? Her origin is pretty convoluted as well (Another reason why I like Julia better.). How long was she a Skrull for anyway? Thanks.
Freedom Force was the government's team. It had nothing really to do with mutants. Julia Carpenter was just working for the government.
Avengers #238-242 explained Jessica Drew's return. With the help of Strange, she got her body back from LeFay, but she sacrificed her powers (of course, her powers returned much later).