Based on the search results, it is unclear what specifically happened to Mei Mei in Jujutsu Kaisen. However, there are several events involving Mei Mei that are mentioned in the search results:

• In September 2023, Mei Mei and her brother Ui Ui are seen in a hotel room in Kuala Lumpur, Malaysia, having escaped Geto off-panel using Ui Uis cursed technique.
• Mei Mei had to face a special grade disease curse summoned via cursed spirit manipulation after killing Pseudo-Getos assassin.
• Mei Meis image among fans was damaged due to her actions during the Shibuya Incident arc, where she flew away from the battle and didnt seem to care about the thousands of people dying in Shibuya. Additionally, she emotionally manipulated her brother to worship her and use him as a tool in combat, which could potentially end his life at any given moment.
• Mei Mei is considered by some fans to be an unnecessary character in Gojos Past arc, as her involvement in the arc seemed unnecessary to fans as she offered next to nothing to Gojos past.

It is worth noting that none of the search results explicitly state what happened to Mei Mei in Jujutsu Kaisen, so it is possible that this information is not available in the search results.