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.

After literally years, M4 demonstrates WHY SHE IS THE HEROINE and becomes METAL GEAR.

She keeps all her old benefits but has 5 star multipliers and better stats now. This gets even better when Mod3 when she gets a unique that ups her firepower and ALSO gives her armour, so she can kinda tank in a pinch. Her buff tiles are ALSO slightly improved. Her mod 2 skill also tags enemies and enhances the mod skills of other Anti-Rain units.

The big thing however is the desperation mode. At mod2 onward, when 3 or fewer allied dolls are in battle (you can retreat 2 units to force this, or simply deploy her with a partial strength echelon), she pulls out the portable cannon and proceeds to deal hilarious damage that makes grenadiers wet their pants, as huge AoE blasts firing from every dummy. The blasts are kinda 100% accurate (the main hit can never miss, even at night, but the splash damage can. Its weird), and can partly crit (its complicated), and is meant to be a last ditch thing to save a fight under dire circumstances (of course, we instead abuse it). This is however, a doubled edged sword, as her RoF also goes down, so its possible for some enemies to slip by if you havent taken this into account.

Basically, Mod her first. She's pretty much priority #1 for modding.

Modded version of M1911

A really expensive trash cleaner.

Basically when she pops smoke, she then goes Alvin York and blasts away 7 times for extra damage, hitting the farthest enemy and working her way closer to the front with every shot. If there are no closer enemies, she just keeps shooting that one until someone else has gotten closer (either because its dead and thus a new thing is closer, or something ran ahead of it).

Note that while the skill has an ICD of 1 second, she doesn't actually start blasting away until 3 seconds in due to the throw animation.