"Chopping hair off is like getting rid of metaphorical and literal dead ends," she tweeted on Friday. "Off with the old and growing the new."
The update comes almost one week after Panettiere, 26, stepped out to support her fiance, Ukrainian heavyweight boxer Wladimir Klitschko, during his match in Dusseldorf, Germany, on Nov. 28. The appearance marked Panettiere's first public outing since entering treatment.
ET was with Panettiere's Nashville co-stars at the Schermerhorn Symphony Center on Wednesday, where the cast was being honored at the CMT Artists of the Year celebration with the inaugural International Impact Award.
Jonathan Jackson, who plays the father of Panettiere's child on Nashville, showed solidarity with his co-star.
"I've connected with her. She seems to be doing really well and I'm really grateful for her that she's taking this time," he told ET. "We're obviously all excited to have her back when the time is right."
Panettiere's character, Juliette Barnes, also struggled with postpartum depression in season three of the series. Speaking with ET in August, the actress opened up about how the storyline helped her better understand what she was feeling in real life.
"What I thought postpartum was, was wanting to cause your child harm. You know, that really severe version of postpartum," she said. "Now, having had a child, I realized that it can be on quite a large spectrum, and the symptoms don't have to be as in your face and obvious."
Meanwhile, another Nashville star is also making waves with a gorgeous new pixie cut and the powerful reason behind it. Clare Bowen opened up about her childhood battle with cancer in an emotional Facebook post last month.
"I don't know if it was brave, I didn't realize that it would have such an impact," Bowen told ET on Wednesday, admitting that she cried when she saw how people were responding to her post. "I just wanted to make people feel better, and it seems to have done exactly what I wanted it to do -- but way more than I expected. ... The way people are speaking with each other, it's been really kind. It's spread exactly what I wanted to spread out there."
For more on Bowen's heart-wrenching story, watch the video below.