She looks like a discount STAR-chan, although it's hard to describe anything that uses a stupidly expensive round like the 5.7 as a discount anything. She has a three second long cooldown and the skill lasts for two seconds. Her big thing is that she can also buff SMGs. She can be used either a mild firepower buff or an actually not awful evasion buff, the downside of which being that getting her evasion buff to work requires moving your dolls around.

3* Ribey.

The problem is Ribey herself is only borderline viable to begin with; she has some of the lowest DPS of any AR herself and almost completely relies on her buffs to make up for it, which usually works out to a net positive, but not always.

Vepr has both weaker stats and weaker buffs (both skill and tiles), and you won't get dupes of her. Really no point in bothering with her, the free SAA you get from career quests or any 4+ star AR will give better results.