Swae Lee's Ex-GF Arrested After Allegedly Headbutting Him

Swae Lee's ex-girlfriend allegedly struck him with her hands and her skull, cops were called ... and she ended up in cuffs.

Law enforcement sources tell TMZ ... the Rae Sremmurd rapper and his ex, Marliesia Ortiz, had an argument at Swae's home outside L.A. in early August, and she allegedly began throwing objects at him.

We're told Ortiz then went on the attack -- striking Swae and delivering a headbutt -- before his security kicked her out.

According to our sources ... she actually then called 911 claiming Swae sexually assaulted her, but when cops arrived she changed her story. We're told Marliesia admitted to starting the altercation by breaking items in his house and hitting him, but claimed the rapper also strangled her.

However, we're told neither Swae or Marliesia had any visible marks on them, but based on the evidence ... cops decided to arrest her.

The L.A. City Attorney has decided to hold a City Attorney hearing with both parties over the incident, but so far ... no charges have been filed.

Interesting note -- Marliesia told us she was done with Swae back in March, and accused him of cheating and being verbally abusive. Seems like she wasn't done with him for good.