How were your rates? Or did you throw Shypys at it?
I'd use my extraneous Shypys on mine if I had a Sakuya...
I fed around 10 dupes for one skill up a while back when Ilya was in 10x coin Descendeds. Gave up on that and started throwing every light pii at her after A.Sakuya arrived. Probably could have finished a month ago if I could find the rest of the light piis in my mail box.
I didn't have any decent light cards to pii besides her, so I figured it was worth it. Of course, after I was halfway done I got A.Thor and pulled Saria and Amaterasu. And now Ilya drops in the co-op 99 stamina God Rush, though I'm not sure about the rates there and I doubt I would be able to consistently farm it without help.
Happy she's done either way and now I can slot her into several other work-in-progress light teams.