"Me and my bestie @itstroyjensen! Happy Holidays!" Bynes tweeted alongside the cheerful photo.
In the pic, Bynes -- rocking long, bright blonde locks and a sexy black lace top under a leather jacket -- is all smiles she she poses with her "bestie."
A source tells ET that Bynes was spotted shopping by herself at the H&M inside the Westfield Fashion Square mall in Sherman Oaks, California on Wednesday night, wearing a white coat and black pants. Bynes later was seen eating dinner alone at a Chinese restaurant in the mall's food court.
"She looked very somber, and lonely," said the source, adding that the outfit Bynes wore in her recent tweet was the same she wore while leaving a nightclub in West Hollywood on Dec. 11.
Bynes' cheerful pic with Jensen is similar to the photo she posted in her previous tweet back in August when she shared a pic of herself and fashion designer Michael Costello.