Since Max Zhang (張晉) mentioned that he was not afraid of anything except for Ada Choi (蔡少芬) spoke in Mandarin, it is evident to reckon the standard of her Mandarin.

Recently, Chinese star Zhang Xinyi (張歆藝) and Ada become good friends after participating a show and she is totally confused when Ada speaks in Mandarin. Subsequently, Xinyi tried to converse with her in Cantonese but Ada kept correcting her and it transformed into an amusing scene. Ada said: “It does not matter as long as you are happy. You will know it once we meet up.” Anyway, both are good friends and love to make fun of each other.

Source: https://www.hk01.com/%E5%8D%B3%E6%99%82%E5%A8%9B%E6%A8%82/595073/%E8%94%A1%E5%B0%91%E8%8A%AC%E8%A2%AB%E5%BC%B5%E6%AD%86%E8%97%9D%E7%AC%91%E8%AC%9B%E5%A1%91%E6%96%99%E6%99%AE%E9%80%9A%E8%A9%B1-%E9%9C%B8%E6%B0%A3%E5%9B%9E%E6%87%89%E8%A6%8B%E9%9D%A2%E7%9F%A5%E5%91%B3%E9%81%93