moatd: Ehm... I dont know which Bipina Cosmos you are talking about, but sure as hell ain mine.
She is a semi skill activation team and she is a WRECKING BALL. The fact she has a bloomed version adds to that even more.
Plus thanks to her slow speed she helps to equalize the team which would rocket itself straight into a boss fight they would not be able to handle most of the times, instead leaving it to the heavy hitters from Team 1.
Honestly cant understand why people hate on her so much. She is a solid 5* with good AOE ability.

NinjaX: Id say keep your money and wait for a gacha that offers a 6*, even if its a random one. In all honesty - 5* eventually become obsolete. As they simply cant compete on the higher difficulty maps, that require you to have multiple rainbows per team. They can barely keep up with full equip slots filled and skill maxed out - plus they need to be cherry picked for best combos possible.

for 46 euros - or 5000 Yen, its not worth it to be honest. But thats just my oppinion ofc.