One thing I was pondering was:
Roberta and Jane had worked together on KQ6, and it was a critical and commercial hit, and obviously in this period Roberta wasn't really interested in KQ anymore (She was busy writing Scary Tales, which eventually became Phantasmagoria) and so wanted to hand off KQ to other designers, while still retaining some role in the series.
You'd think that given the success of KQ6, she'd have wanted to keep that team--her and Jane--together. But instead she brought in Lorelei Shannon, who while like Jane obviously took the series in an utterly different, opposite direction.
It just makes me wonder if Roberta wasn't a big fan of Jane's style or where Jane was taking the series, or--perhaps--if she felt upstaged by Jane. I mean usually if a team is successful, you keep them together, you don't dump the other half of the team the next year to bring in somebody brand new.
With KQVIII, it's obvious that for whatever reason, Roberta was interested in KQ again--I guess because she had gotten Phantasmagoria out of her system--and decided to take full control of the series again, so there isn't really as much question about why the lack of Jane.
This isn't a slam at Lorelei Shannon, as I love KQ7, but just a speculative thread.