That's fair...

but being turned in to a construct from something else, will most likely alter the way people react to you in a negative... ergo: -2 charisma is perfectly in line with your story.

A story like the one you want should (IMO) come with some numerical effects for your character.

Maybe talk to your DM about making a pretty (no -2 cha), but clumsy(-2 dex) warforged, "because she lost some sense of balance in the change, but she's still just as funny..."