As for how Jen could've possibly slipped inside ... law enforcement sources believe she still had a key to his place. We're told there were no signs of forced entry.
Step one for any breakup ... change those locks!!! Can't say Gloria Gaynor didn't warn ya.
TMZ broke the story ... Ronnie filed for legal protection against Jen after the alleged attack, claiming she was enraged after finding another woman's makeup in the trash.
We asked Jen's attorney, Lisa Bloom, why Jen was in Ronnie's home and she says ... "You ask a good question, and there is a good answer, but we will be presenting her position in court, not in the media."
Jen's attorney adds ... "she has not been served with any restraining order, and any contact the two had in recent weeks would be a clear violation of the restraining order against Ronnie."