I don't care one iota whether she is dating the rich guy or not. But why are people so sure? There has never been any confirmation.
Jisoo and Jennie are the only BP members who have confirmed relationships. Jennie and Tae is the only one not officially confirmed, but there was concrete proof after people invaded their privacy.
There has been no confirmed relationship for either Lisa or Rosé, but people talk as if Lisa herself has told them she is with this guy.