Lindsay Lohan surprised on-and-off girlfriend Samantha Ronson by showing up at her birthday party in Chicago, fuelling speculation that the tumultuous twosome is back together.

The pair had dinner with Lohan­’s younger sister, Ali Lohan, before heading out to catch a concert at the Hard Rock Hotel, according to Page Six source, who said, “Lindsay was being horribly loud.” The pair headed to bar where a source saw them “fighting over which drink belonged to whom.”