So. Spider-Woman #37-#38. Jessica Drew wants to get a P.I. license, and is trying to persuade Nick Fury to be a character reference, but without admitting her name to him. (hmm, a superpowered private detective, there's mileage in that idea.) She is caught in a scheme by Black Tom, the Juggernaut and Black Tom's niece, Theresa, using the codename Siryn. She is Banshee's daughter that he never knew existed and gets rescued from their clutches, obv, but is mostly there as a story hook. The X-Men arrive, tracking her on Cerebro (it still being early enough that they seem to be following every lead they can, even though we'll later find out this cannot be true). Siryn's relationship with her father ought to be part of this, but it will not be immediately explored: Banshee isn't even part of the team at this point. Siryn makes a brief appearance in Uncanny #148, but then is just forgotten about, and won't appear again until 1987's Fallen Angels.
Her absence from New Mutants is difficult to explain. One could make the case that Moira wouldn't send her not!stepdaughter to the Westchester meatgrinder... except that she did send Rahne. And why did the Mutants never meet her when they visited? They even met Jamie! In this context the fact that Michelle vanishes makes a lot more sense.
Incidentally, I found the use of a character called "Ben Disraeli" in this story really distracting. Imagine if a British comic called a character "Ulysses Grant" and then didn't have anyone make any jokes or references to it.