Passively, she's Mk23 with better tiles. Regarding her active abilities, she isn't as nice as Mk23's straight damage upgrade for some, but better for others (such as fights with Grape that require her to shoot faster). They're similar but not interchangeable so you'll need to use the space between your ears.

Also she's kind of boring and has no easy jokes besides the Viking name, which doesn't suit her at all, so blah.

Babushka says not one step backward. Every seventh shot, she gives a damage bonus! Also, the thing starts active, making her one of very few buffers with a start-of-battle skill activation. Her first skill is still defensive in nature, and the percentages got bigger. She's actually useful in a number of situations, either for reducing enemy firepower in specific fights (usually Gundam or tank related) or just the straight DPS boost from the get-go. You only really need her up to Mod 2, but the Mod 3 art is cute.

Her pre mod form is here