Hmm, looking at Ooki's past actions in previous chapters there are 2 ways you can interpret her feelings:
1. She gets off or gets a weird kick out of seeing Katagiri squirming when she sees Okada's suffering face, thus developed a yuri attraction (god I hope not). That's why she always asks "Did you feel good?"
2. She also likes Okada, but to an extreme degree (bordering or within yandere levels). Here's why I think that:
Don't you find it odd that she knew things from his past such as the pet he had as a kid? Furthermore by this point based on her super human abilities you'd think she'd be constantly aware of him looking at her boobs but she let's him look anyway. In another chapter she forced the delinquent girl to wear bandages around her boobs because she didn't want another Big Boobed girl getting Okada's attention. During Okada's troubles with the Yandere-Bitch she voluntarily sat next to him to get in her way which you can interpret as helping Katagiri, helping Okada, or satisifying her own desires. In the shrine chapter she also stalks Okada and Katagiri based on the Yandere-Bitches photo. Also in another chapter she forced Okada to smile while Katagiri was walking by, don't you find that strange, almost like she wanted to make Katagiri jealous and backdown.