Can you blame her? She is traped in disfunctional relationship with Wade who doesn't have need to acomplish anything in his life exept of videogames or get out of his comfortable bubble despite all Cindy attempts to shake him a bit. Of course she would be jealous of Lena, the girl is three years younger than Cindy yet doesn't strict herself in what she is passioned about and live her life as she pleased! Thats the kind of thing Cindy want for herself yet when every time she tries Wade comes by and forbid the pursuit by wining or complaining.
They're both bad tbh, they have nothing in common and their relationship wouldn't last anyway with or without Ian/Axel interference...
for the record Cindy is also always whining or complaining and tries to impose her needs on the group like trying to go to a different bar that none of her friends wants to go to and gets mad when no one wants to accompany her and when Ian does go with her she gets angry when he refuses to pay for her drinks ??!!! like seriously ?? she's the one who wanted to go there....
Anyway that's just Cindy's character, it's who she is it has nothing to do with wade. Plus nobody is forcing her to be with him she can just dump him and go pursue her dreams or whatever instead of blaming everyone else like she always does.