Offset's Alleged Mistress Summer Bunni Gives Tearful Apology to Cardi B

The woman with whom Offset allegedly cheated -- not long before Cardi B gave birth -- says she's remorseful, and tells TMZ ... she never wanted to be a homewrecker.

Summer Bunni cried openly while telling us how guilty she feels after word got out her hooking up with Cardi's husband might have been a catalyst in the couple's split. SB is the woman Offset allegedly asked to arrange a threesome that would include rapper Cuban Doll.

Summer tells us she hasn't messed with Offset since Cardi had their baby, Kulture, but still feels ashamed for playing any role in breaking up their marriage. She insists she didn't know how serious Offset and Cardi were -- which seems absurd. They were married!

Bunni hasn't spoken directly to Cardi, but she tried to deliver an apology through us, and says she hopes the estranged couple will reconcile.