你这个句子里从句太多,有点罗嗦,应该改成
She told us that she hoped to become a pianist.
她告诉我们她希望成为一名钢琴家.
这个句子只剩一个宾语从句,从句中后面用不定式作宾语.
有不明白的请继续追问,嗯，谢谢，顺便问一下，请问这个样呢？She told us her hope is that she would become a pianist也可以吧，不过还是宾语从句中又带一个表语从句，总之比你前一个理顺多了。