Dee Devlin just went scorched earth on Conor McGregor's sexual assault accuser ... lighting her up in a series of Instagram posts on Tuesday afternoon.
In the IG Stories, the UFC superstar's longtime partner called Nikita Ni Lamhain -- who just won her civil case against McGregor in Ireland last week -- a liar ... and said straight up, "My sons will be warned women like you exist in the world."
Devlin claimed that back in 2018, prior to Ni Lamhain's suit against McGregor, Ni Lamhain would send "messages and pictures of herself over and over to my man" .