Brian Hickerson Allegedly Sent Woman Flirty DMs Months Before Hayden Panettiere Died

Hayden Panettiere's boyfriend was allegedly sliding into another woman's DMs just a few short months before Hayden died.

Here's the deal ... Page Six published a story Thursday reporting on alleged messages Brian sent to an unnamed Greenville, South Carolina woman in March ... roughly 5 months before Hayden's tragic death in Greenville.

This woman allegedly met Brian at the downtown nightclub the Cat's Pajamas on March 28 ... though she admitted to P6 she was "heavily intoxicated" the night she allegedly met Brian and didn't remember much.

On March 29, Brian allegedly DM'd the woman, "Great meeting you last night pretty lady. I owe you a date. I’m heading to [C]ity Tavern for a slushie in a bit you should join."

She says she replied on April 1 ... apologizing for missing his DM and telling him she didn't remember much about their first encounter.

He provided some context in another alleged message ... writing, "You wanted to make sure I took you somewhere nice on a date which clearly throws Waffle House out the window so I guess Halls [Chophouse] might have to do if you wanna meet each other properly."

Brian allegedly continued, "Just moved here from Los Angeles so it was nice meeting a pretty girl in Greenville out of the blue. I also realized after I reached out on instagram you gave me your number so I'll shoot you a text if that's better."

Ultimately, this woman says the two never met up ... she was only 25 when he allegedly messaged her -- Brian was 37. The age gap and the lack of memory from their first meeting proved to be dealbreakers.

As we reported earlier in March, Brian was seen helping Hayden while she was on crutches at LAX -- but we were told at the time the two were just friends.

In the aftermath of Hayden's death, we learned the pair were in a relationship for years ... with friends even laughing at the absurd idea that they split. Hayden distanced herself from Brian in public to help her image, but they were never as on-and-off as they made it seem in the media.

It's unclear if they had an open relationship or some other sort of arrangement ... though it's worth noting this anonymous Greenville woman said she had no idea the two of them were together.