If you wanna a tip, try a bit magnet card so you can get a lot of bits quickly while you kill enemies. With 150ish bits collected, you can get the ball quite fast, fast enough so luring enemies to the other side of the map gives you enough time.
But yeah, I would agree, Ciella's Challenge feels way more difficult and unfair compared to Meira's Challenge. I think the biggest problem is the never ending pression. If it take a little longer to enemies respawn, we could get a little of pression off, and have more time to get the ball. For sure it would feel better.