I have read this sentence and got slightly confused.
When my mother, who was only 18 when she had me, told me I should wait until I got older to marry Lucy, I knew she was really happy I met the right person.
— Adam from engvid.com via Wikipedia Republished
In this sentence when my mother is an adverb clause and who was only 18 she had me is an adjective clause.
I know an adverb can modify an adjective, but not vice versa. I believe in this sentence that an adjective clause is modifying an adverb clause.
I am curious to know what this adverb clause is modifying.