Hmm. In my opinion, she lacks what I like to call, the mutant 'advantage'.
IE, she's only human. She's not highly trained, nearly mildly athletic, she's vulnerable to everything normal people are, with the exception of projected energy in when she's Energizer, or well, most anything else when she's in cloud form, except Vaccums. (Of course she can't hurt anything while her mass is that thin either.)
Note, switching powers requires the presence and usually the cooperation of one of her siblings, all of whom have normal lives now, and two of which live out of state. (Her sister has a loft in New York)
With the Starstreak powers, she dodged well, and with the Counterweight powers, she could hit things very hard, lift heavy objects, and float people and objects around... again none of which stopped someone from shooting her.
So, really, various weaknesses.
A list: Energizer: Only Human strength, won't disintegrate living beings. (Ever. Even to save herself or her family... a true weakness.) Energy Blasts use up he power quickly unless she disintegrates something else, and will only use weak blasts against human targets unless the target shows resistance to the power. Vulnerable to all normal attacks, even a punch to the face.
Starstreak weaknesses: Only normal human strength, toughness, countered by high maneuverability, and near speed of sound velocity. Flight path very visible, all other human frailties present.
(The other two powers will be available least often, as both her brothers now live out of state.)
Counterweight Power weaknesses: Seemingly superhuman strength is
countered by the fact that a good crack to the jaw from a normal person is likely to hurt her normally if she isn't floating at the time. Vulnerable to pretty much everything a normal human is, though
with much more mobility.
Mass Master power weaknesses: High Density form is hard to hurt, (Though not at all impossible, more like rock than steel.) Can't move quickly in this form, and normal human strength plus no leverage means she's fairly helpless as a combatant, except when using the old 'jackhammer' technique, a power that isn't very useful unless a 120 pound weight falling on you is dangerous to you. Helpless to do more in cloud form than shield people from view, it is at least, very hard to hurt in return.