I could also see her really liking Aurora.
Eilonwy is feminine and has a quieter strength- I think she would like the dignified defiance of Cinderella. Eilonwy would like Cinderella's strong spirit and how she fights against her stepmother in her own quiet way, as well as how she goes out to the castle for the ball. I think she could relate that to when she freed herself in the prison and ended up exploring the dungeon. Eilonwy would definitely prefer the more feminine, refined princesses.

She'd love Tiana's sarcasm, but overall I think she'd find her boring.