It has been a while since the 'Twilight' co-stars, Kristen Stewart and Robert Pattinson, ended their relationship, but new reports are claiming that old feelings are stirring up again. Rumor has it that Pattinson is publicly flaunting his relationship with singer FKA Twigs, which doesn't sit well with Stewart.

"Kristen knows about Rob and Tahliah. It's bittersweet," an insider told Hollywood Life.

While Stewart is delighted about the fact that Pattinson is happy, reports say Stewart is still hurt because it appears Pattinson is serious with his new girl.

"I mean she's happy that he's happy, but it stings. She knows it must be serious if he's being affectionate with her in public. She knows he's ultra picky and wouldn't hold hands with someone for the world to see unless he was really into her," added the insider.

Stewart is still reportedly sensitive about the issue, and she seems to be uncomfortable about the fact that Pattinson has fallen in love again.

"Let's just put it this way, Kristen is just glad she's not in LA. The last thing she would want is to run into them. It's just weird still. Still a sensitive issue," said the source.

Pattinson and FKA Twigs have not confirmed their relationship yet, but they have been spotted publicly displaying their fondness for each other. Reports say that Pattinson and his new girlfriend have shown more public displays of affection in two weeks than Pattinson and Stewart had shown in three years of their relationship.

Reports say that Pattinson is crazy about his new singer girlfriend, whose real name is Tahliah Barnett.

"Rob is so crazy about Tahliah that he wants to show her off to the world. He's proud to show her," a source told Hollywood Life.

The source also added that the 'Remember Me' actor even brought Barnett to places where he brought Stewart.

"He's been taking her to his favorite hangouts, like No Vacancy, to listen to music; places he used to go to with Kristen [Stewart]," the source added.