Well, yeah, since the normal one unraveled, the Shadow Weave did, too.
Oh, crap, I forgot to say that part before. I goofed it up. Shar didn't actually like...create the Shadow Weave, it was more that she like discovered a different part of the Weave or found like something akin to the "shadow" of the Weave or its dark side or something? I dunno. But basically, the Shadow Weave is intrinsically a part of the Weave, so when it was destroyed, so was the Shadow Weave.
Which once again makes me wonder why they thought it was a good idea. Character wise, I mean since SharSpoiler: did thiswas the on, conspiring with Cyric, who killed Mystra. I mean it's not like her and her followers didn't use the Shadow Weave plenty and she should have remembered magic getting all screwy the other five times Mystra was killed