The first 6 star SMG, and oh boy, she deserves it. As long as the damage isn't so overwhelming that it can kill her dummies outright, she has a chance to negate the damage. The chances increase if the enemy has more debuffs or has Marks of Vengeance on them, which immediately makes her a good pair with M4. Also the Sop doll is cute and comes with weird features. This is literally Sop's fault.

So if it hasn't been said enough, absolutely get the Mod1 the very second you can. It's 200 fragments and some cores for a fair boost in performance. Extra stats, a bit more FP buff on her tiles, a little extra HP, and an improvement to the slowdown effect on the smoke.

The real problem is her 2nd skill is janky and not extremely practical. It's a little bit of a bonus, but not likely to make or break a fight. So yeah, the Mod2 isn't great. The mod 3 however, gives her a unique equipment that goes in the suppressor slot and is basically a suppressor with better stats (+5 EVA over normal) which helps her tanking ability somewhat. Whether this is worth it up to you, but definitely get the Mod1 at least.

The rest of this is basically the same song and dance where she has top class offensive buffs that continue to remain unmatched among SMGs, so you WILL likely continue to use her.