你可以说："Although she is more serious than me," 或者 "Although she takes a more serious approach than me."
这个短语的来源可能来自拉丁文 "serere"，意思是 "to bind or join together"，后来发展为 "to be serious or grave in manner or speech"。
下面是一些英文例句和它们的中文翻译：
"Although she is more serious than me, I still enjoy spending time with her."
虽然她比我严肃，但我仍然喜欢和她在一起。
"Although he takes a more serious approach to his work, he can still be quite funny at times."
虽然他对工作很认真，但有时候他还是很风趣的。
"Although she is generally more serious than her sister, she can still be quite playful at times."
虽然她一般比她的姐姐严肃，但有时候她还是很嬉戏的。