X17 XCLUSIVE - Lindsay Parties Too Hardy!

...until 5am! Ugh, Linds, you're killin' me.

Former promising actress Lindsay Lo has nothing else to do these days (especially considering that her ex Samantha is outta town) than party all night long... and last night at the Chateau Marmont, that's exactly what she did!

An X17 inside source tells us that LiLo, Dina and Ali - yeah, WTF! - all showed up at 11 pm and stayed until 1 in the morning. Linds "looked like a mess. Her eye makeup was smeared as though she had been rubbing her eyes. She smoked cigarettes, talked on her phone and didn't drink any alcohol."

The source adds: "She had a permanent scowl on her face the whole night." Hmm, guess she's still not getting along well with her mom!

Between 1 and 5 am, Lindsay had an afterparty at her pad - yeah, doesn't sound like the best idea to us either! An X17 photog on the scene heard a lot of talking from inside the house, including a couple "stop, mom!" and "mom, do NOT say that again!" from LiLo all night long...

Also, while it's nice to see Lindsay in a dress and not leggings, all it makes us realize is how skinny she's looking. Eat something!