So. What's the deal with that big doll in the black dress?

[Tails' Cash Explosion]

The one that was behind display glass and then broke out of it. Does she literally never actually show up anywhere as an enemy?

I was really hoping it was going to become a stalker in some of the main areas of the mansion...

[Dark Messiah]

She shows up if you save the disabled doll by fighting monsters downstairs in a basement.
Can't say what happens because of spoilers

[Tails' Cash Explosion]

Oh. I did that. A little disappointing, oh well.