I think you're overselling it as a hookup app, I presume you're referring to the 摇一摇 feature? In any case, it's a texting-first hookup-distant-third sort of thing. Like my contact said, it depends on the intent of the user. I'm so curious why your wife is so suspicious!
If I was going to point out a Chinese app for basically hookups and nothing else, it'd be 陌陌。That thing is pure, 100% Tinder/Grindr.
I always thought 陌陌 was only a hookup app, but was recently told that it started as a way to connect people with common interests (e.g. I could use it to find nearby python users or nearby HN users.)
Fair enough. My wife won't let me go near WeChat even if she uses it herself (I'm happy to oblige, I'm not much into chatting). Some of my expat colleagues on the other hand...
If I was going to point out a Chinese app for basically hookups and nothing else, it'd be 陌陌。That thing is pure, 100% Tinder/Grindr.