Consider this reaction: Just as casual sex is not necessarily inherently harmful, neither are online affairs.
But they may be so when participants are also involved in another primary offline relationship, because of the harm imposed on those partners.
I feel very disgusted by it, and I'm very doubtful about our relationship to keep building up. Maybe somebody is going thru the same and would like to exchange a few stories etc. (3) (a) If it bothers you what she did on her own time - leave. (b) Get it on and see if she'll do some pole dancing for you.
Since she has this desires for people that are not just random on the online world, but they are actually people she knows or met in person. (4) You sound very possessive - that's never a good thing.
Online sexual activity can involve various activities, such as viewing explicitly sexual materials, participating in an exchange of ideas about sex, exchanging sexual messages, and online interactions with at least one other person with the intention of becoming sexually aroused.