Need advice on my friends relationship situation ?

Throw away account ; My friend 24F ( wants to be an independent woman) got back with her LDR Ex 26M. I’m watching her mental health tank. How do I handle this?

The Background:

My friend and her ex were together for about 4 years. The first 3 years were in person during undergrad and moved to a foreign country for higher studies . but as soon as they transitioned to a Long-Distance Relationship (LDR) in the last year, things got incredibly hard and they had a massive breakup. Since then, they’ve been on-and-off 1 to 2 times. Recently, they officially got back together (still LDR), and she is keeping it highly secretive.

The Core Issue: His Behavior

When they went long-distance, his anxious attachment turned into severe coercive control. Even though they are hundreds of miles apart, he tries to micromanage her life. Some of the things he does:

• Policing her clothes: He fights with her over how she dresses, specifically bodycon or sleeveless dresses. He accuses her of "wearing them to show everyone her beauty." (The hypocrisy is that his own sister wears sleeveless dresses and he doesn't care).

He doesn't want her talking to any guys and accuses her of "letting them talk to you," effectively cutting her off from male friends.

• The Digital Leash: He demands immediate responses for his texts

• Backchanneling: When they were broken up, he went behind her back to her friends to keep tabs on her, which ended up causing a fight and fracture within her friend group.

The Current Situation: Not sure whether he has changed . She wanted to try one more time And they did few months ago and didn’t work out not sure what the reason was . Now they are back at it again .

she didn’t share much details as I’m opposing this.

. Does the controlling partner ever actually change, or is he just masking during this "reunion" phase? How do I support her without validating him? Reddit recommended “Why does he do that “ and seems his behavior is kind of abusive . I want opinion from fellow redditors and used AI to enhance the writing .

TLDR; my friend (24F) secretly got back with her LDR ex (26M) after a difficult breakup. He exhibits controlling behavior policing her clothing, isolating her from male friends, demanding constant location attention, and even reaching out to her friends behind her back to monitor her during their breakup. She keeps the relationship secret and hides her phone. I want to support her without validating his behavior. Is this abuse, and how do I help without pushing her away? TIA and appreciate your opinion.