Lily Allen ‘Dating Again’ After Treatment and David Harbour Split: Source (Exclusive)

Lily Allen is getting back out there.

The “Smile” singer and ex David Harbour separated after four years of marriage, PEOPLE confirmed in February, and she subsequently spent time at a treatment center for both group and individual therapy. Now, a source tells PEOPLE she’s reentering the dating scene.

According to the source, Allen had a crazy rough start to the year, but she’s doing better now after spending time in Europe this past summer.

“Her marriage had been crumbling for a while, and it put her in a terrible mental state,” says the source. “It was very stressful and sad. Lily is a fighter though.”

The source continues, “She spent time in Europe this past summer, is casually dating and doing much better. She’s focused on her [daughters daughters Marnie, 12, and Ethel, 13, shared with ex-husband Sam Cooper] and is starting to feel like herself again.”

Over the past few weeks, the “Trigger Bang” musician stepped out to several events in London, including a Chanel lunch, a Perfect magazine party and the West End opening night of Clarkston.

Allen previously spoke about seeking treatment on the Feb. 13 episode of her Miss Me? podcast.

“I just feel very grateful to have been given the time and the space that I needed. I went into a sort of treatment center for a few weeks, which was great,” she said at the time. “I did a lot of group therapy and some individual therapy and I just, I needed some time and space away from everything.”

In treatment, Allen explained, she did a lot of shadow work about her “inner child stuff,” and while it “was not easy by any stretch,” she knows healing is a “lifelong journey.”

The “Hard Out Here” artist explained that her decision to seek treatment was with her children in mind.

“I absolutely adore my children and I’m in a situation now where I really have to be my strongest self for them. And I felt like it was getting harder and harder for me to be able to show up for them in the way that they need me to,” she said.

Allen continued, “It was a really big decision to have to leave them for a few weeks to go and focus on myself, but ultimately it was for them. Yes, it’s for me, but it’s for them so that I can get us through this bit. I needed some help to be able to do that.”

She detailed choosing to seek treatment in the midst of “emotional turmoil” and told fans she was “definitely in a stronger place” following the experience.