Felt bad that no one posted it yet and I didn't know if you looked for yourself, but it's currently on Page 5 of the Penance gallery on ComicVine: http://www.comicvine.com/hollow/29-10573/images/?page=5
You can see some other scans from that flashback on the same page. :)
In addition to the 1+1=3 theory (i.e. the whole is greater than the sum of its parts), Monet may've been acting differently because she was traumatized. Peter David has implied as much in issues of X-Factor, I believe.
I'd like to think that what we saw in Generation X was the traumatized true Penance having control of her own body, because Monet lost control at some point, and that after she was freed of Monet and the twins, she became more confident in herself and her friends (Jubilee, in Annual '99, describes the new Penance as a pitbull, while the old Penance was a house cat).
I like how Hsien-ko's claws are kind of like Penance's and you're right, she does have a haunted background, too. My fave Darkstalker is Felicia, though. ;)