Omg Ataru, are you sure you're the same age as Elly pfffffffffft
Wanko though, be careful with what you say, you might hurt Sakuma's feelings.
But after the flashbacks, it actually makes a lot more sense why she's acting like this. She basically proposed herself as a trial, a temp for Sakuma after her bad breakup. A change of pace from guys. Deep down she's probably afraid of the possibility of Sakuma ending things because she found another man that she likes and that likes her back. We as the audience know it'd never happen, but that's only because we're privy to Sakuma's thoughts and also her actions when Wanko is absent.