Momo is a character she created with chat then made a model and rigged on stream. Bea used a voice changer when playing her character. So it's likely Bea, but im not going to get my hopes up on a return.
Oooh, interesting. Twit is just a clip from that stream, so literally anyone could've post it. Though if her known friends repost it, it's her or some friend adopting the character.