How to stop stalking her?

I know everyone says this, but this is not about me.. It's about my cousin.

Her now ex husband cheated on her with a coworker July of 2022.

He said it was just a drunken mistake, but my cousin called the other girl and she confessed he had been heavily flirting with her since she started to work there.

From what I know they all went to happy hour, the guys took the girls home instead of just getting them an uber, she sat in his lap and I guess they started getting handsy and that's when everything started.

They've been together ever since him and my cus separated so it was obviously not just a "drunken mistake."

Ever since, my cousin won't stop checking her socials daily, she has pictures of her, loves to hear when people bring her up, especially if it's bad stuff.

I told her to stop and block her but she tells me she can't stop imagining the things they must do sexually and how great she must be in bed.

I feel like she's constantly comparing herself to her. "I can't believe he left me for someone so cringe" "Look at this post, she's such an attention seeker", "Do you think he preferred her cuz she also likes to go to the gym?" It's so unhealthy, she gets a fix but then is crushed.

She showed me pictures of this girl being "filtered to the max" and when I asked how she got them she said she made a fake Snapchat.

I love her so much, and I feel so grateful that she's so honest with me so I don't want to be harsh and have her see me as someone who's judging her, cuz I'm not.

I just can't reason enough with her that this is keeping her from fully moving on. If I saw that her stalking this woman was benefiting, I would let her do it. But like I said, when she's verbally tearing her down It's like she's on drugs, but then next day comes and there she is on the apps again.

How can I get through to her without having her wall up?