Stheno

You would need her 10/10/10 to be functional, unless you bother to do that, you know what you are doing and know how to use her properly, don't.

No

She has the niche of being a anti male servant, but even in that aspect she's below par compared to euryale and orion, with her buster np dealing no damage and a quick deck. The best uses I can see her having are buff stacking with a divine servant or a charm lock team. I woulden't recommend leveling her skills or even her just level euryale.:D