Khloé Kardashianis still coming to terms with the changing dynamics of her family in the wake of her split fromTristan Thompson.

Weeks after Thompson, 28, was allegedly involved in acheating scandalwithKylie Jenner‘s best friend Jordyn Woods, a source tells PEOPLE that theKeeping Up with the Kardashiansstar, 34, is feeling bitterness towards her ex — specifically surrounding the lack of time spent with their daughter, 11-month-old True.

On Wednesday, the NBA star celebrated his birthday, but a source tells PEOPLE he didn’t spend it with the former couple’s little girl.

“Just in general, he isn’t spending much time with his daughter. It’s very upsetting to Khloé. To her, True is the most important person ever. It’s very difficult for her to understand how Tristan isn’t willing to make more of an effort to spend time with True,” says the source.

Tristan Thompson/Instagram

khloe-kardashian-1

“It saddens her that True doesn’t have a very close relationship with Tristan. Khloé has always done everything she can to encourage Tristan to spend time with his daughter,” the source adds.

“She just doesn’t understand it. It’s very disappointing to her.”

Last April, just days before Kardashian gave birth, photos and videos surfaced of Thompson getting close to other women. Though the new mom initiallyforgave the basketball player, but she ultimatelydecided against moving to Clevelandin the fall to be with Thompson. They remained together, but in the new year, their relationshiptook a downward turn, living apart and spending barely any time together.

“Tristan never really acted like he cared after Khloé decided to not return to Cleveland after last summer,” adds the source.

Seth Browarnik/Startraks

Khloe Kardashian And Tristan Thompson at LIV at Fontainebleau

Now, Kardashian appears to be trying her hardest to move on from Thompson — and she’sletting it be known.

On Thursday, she posted a series of inspirational and cryptic quotes on her Instagram Stories, including one about how to “forget” someone, just one day after Thompson’s birthday.

“There’s really no shortcut to forgetting someone,” the quote read. “You just have to endure missing them everyday until you don’t anymore.”

Another quote said: “Be the kind of person who isn’t afraid to ask someone if they are okay twice if they say they are, but look like they aren’t. Be the kind of person who smiles at people even if they don’t smile back. Be the kind of person you wished for when no one was there for you… Be that person because people like that are rarer than the rarest diamonds and gold.”

“Everybody always asks if you have a career, if you’re married, if you have children,” a third quote read. “As if life was some kind of grocery list. No one ever asks us if we’re happy.”

One day later, though, Kardashian softened her tone and placed the fault instead on Thompson.

“This has been an awful week & I know everyone is sick of hearing about it all (as am I). I’m a rollercoaster of emotions & have said things I shouldn’t have,” she tweeted. “Honestly, Tristan cheating on me & humiliating me, wasn’t such a shock as the first time.”

source: people.com