The defining relative clause tells us which skirt.

限定性定语从句告诉我们是哪个短裙。

Remember that defining relative clauses are used to add important information. The sentence would have a different meaning without the defining relative clause.

请记住，限定性定语从句是给句子增加了重要的信息，句子如果没有了定语从句，其意义不同。