Dan Jurgens (Take One Vol. 1):
The first time Michelle makes her presence known is (ie. not in non-speaking flashbacks) when she comes to save her brother from being put to death. That in it's self is a pretty bold statement on her character. A little later on in the series (18 to be exact) we learn that gun control is strict making the firearm she came with highly illegal. Despite it being a risky situation Micelle keeps her cool and even tells Booster (who she hasn't seen since he was kicked out of the house) that they can talk later. When he demands to talk then and there she calmly explains that they already learned of his heroics in the past. His familys' proud of him and all is forgiven.
She's spunky, able to easily parry her brothers' comments in a way siblings are used to. When it comes to Skeets she doesn't have Boosters' emotional connection. While he worries that she hurt Skeets feelings Michelle shrugs it off since Skeets is just a robot. When she takes the Goldstar costume Michelle doesn't bother to run it by Booster or Trixie (who she considers to owner even though Trixie has no interests in it.) She has a pretty good idea that her brother wouldn't want her to take it and steals it anyway. Michelle doesn't seem to be testing the suit out for a future as a superhero but rather to see what the appeal is. She assumes the seductive power it brings is what got her brother interested in his career as a superhero.
After she's taken a worried Booster tells Skeets that they were never as close as most twins growing up but reached a tighter bond recently. Despite being dead tired, she tells him to protect their escape as she does the more dangerous task of accessing the panel to turn on the teleporter. This Michelle seems to know who she is, cares for her brother but not to a sappy extent. She's not as emotional or unsure of herself as Booster is. Michelle might not be great at using the suit but she's brave and makes her own choices without needing to consult anyone.