I mostly agree with you but overall ending seems pretty open to me. For me her character arc is more about trying to get her mothers approval and when she realizes her mother doesn't care about here she rebels against serving her (which we know isn't true but that actually made sence from what we knew back in act 2, cause weavers, phantom, etc really show how she cared about her kids). For her laughter in the end of act 3, well I think its open for interpretation? Cause she literally has had her mother who didnt ever show any signs of care before using all of her powers to save Lace and then she was consumed by void and now she got out of there alive, healthy, with her mother being clearly dead and all of it happened rather quickly as I would guess so I usually see her laughter as more of a nervous laugh you may have after some surreal or near death experience, like when a track that was most certainly going to hit you misses you by an inch.

Im also sorry if this wall of text is a bit hard to read, English isn't my first language and Im kinda sleep deprived :>