The few friends Joan had made there were all invited to her birthday party.怎么翻译？

Joan had made there 是 定语从句 修饰 friends 省略了 先行词 that/who/whom
所以可以翻译成 Joan在那里交的为数不多的朋友都被邀请到了她的生日聚会中。

琼在那里的一些朋友都被邀请参加她的生日聚会

Joan在那儿交的很少的朋友都被邀请去她的生日派对。