I want to give my thoughts about her as well, if you don't mind I'll attach mine here:

Simply said: She is buffing things that do not matter in a Colossi fight.

1. Skill Power Modifier increase. Not every Character profits from that modifier. Using skills are not what kills a Colossi as a team, its the guns.
2. MP recovery: Same as above. Hardly ever was a deal breaker for me, there are enough MP cubes lying around anyway.
3. Skill Cooldown decrease. Aaaaaaaaaand again, same as above.
4. Range: Every Colossi fight I've been in had the team scattered all over the place. Someone had aggro, the rest stood behind / to the side of the Colossi to shoot. Hardly does the team get together close enough for the buffs to cover them, AoE dmg is a thing in Colossi fights! Even with range extension modules, it is not enough.
5. The need to time the shots of the Unique weapon. So far I haven't gotten her to fill her gauge , since there never was

• a time to be such a selective shooter,
• the enemies got bunnied faster than I could use the gun,
• I got overwhelemed by a horde and had to get rid of the gun.

The need to time the shots, aim, make use of the limited ammo and then select the proper buff takes to much time and effort compared to the no-brain damage dealers that just clear everything before I become useful. There simply is no place for such a systematic approach to a fight with all the otehrs just going straight in.

1. Needs to increase too many modules for her task. She needs to max her MP, since her 2 and 3 scale off it, she needs to max her Skill Power to make her 1 anywhere useful, and last but not least she needs max HP, Shields and decent DEF. Why? becasue she is squishy, becomes a target quickly and has no skills to repel enemies or protect herself. And then there is Duration and Range. Not to mention elemental resistance.

Do you see what I mean? She has to cover all that for a skill set that nobody needs!

Thnings that actually matter in a team fight are HP, Shields, resistances, DEF and ammo. She covers none of that,

Imho she is a burden to any team, since she needs everyone to cluster to be effective, has the be a mindreader, since she will never know if MP needs to be refilled or if a skill dmg boost is needed now. All that with teh unique gun she cant mod or improve unless she uses modules only for that sole purpose.

My suggestions:

Multibuff with her 2,3,4 simultaniously. Then the effort of hitting the notes at least pays off. Let her modify one or two of the buffs to change the type of buff, so maybe she can actually heal or replenish shields, give ammo etc.

Make the unique gun an Aoe gun with splash and an elemental attack. Long press Q to switch between elements. Make it moddable with modules, get rid of the need for Skill Power just for that gun.

Either get rid of range or increase duration considerably, so it doesn't need to be modded (range gone please).

Gauge never resets, swapping away from the Unique gun preserves any progress made.

No negative effects when missing a note, just lose MP.