一緒にいてもいーってならない人

What does 一緒にいてもいーってならない人 mean here ?
context: a character describe her requirement when finding a suitable assistant for her sister. Much thanks if some high level JP experts could help me find its correct meaning !
A「姉さんの補佐だから、人選が難しいの」
A「頭が切れて、忍耐強くて、度胸があって、我慢強くて、できれば見栄えもよくて、姉さんが一緒にいてもいーってならない人が必要なの」

zeroh4nter said:

What does 一緒にいてもいーってならない人 mean here ?
context: a character describe her requirement when finding a suitable assistant for her sister. Much thanks if some high level JP experts could help me find its correct meaning !
A「姉さんの補佐だから、人選が難しいの」
A「頭が切れて、忍耐強くて、度胸があって、我慢強くて、できれば見栄えもよくて、姉さんが一緒にいてもいーってならない人が必要なの」

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I think DeepL's translation is good.
A: "It's hard to pick the right person to be my sister's assistant.
A "I need someone who is smart, patient, courageous, patient, and preferably good looking, and who my sister won't mind being with.

If I'm not mistaken, the equivalent grammatical sentence would be
姉さんが一緒にいても良いと言える人が必要なの
but I'm not really sure how the ならない fits in. Maybe something like:
姉さんが一緒にいても良いと言えるようにならなければならない人が必要なの

いーってなる is a colloquial/slangy expression to express a state "enable to endure being irritated".

By the way, that sentence is ambiguous. Grammatically, two interpretations are possible. The one who is not irritated can be both 姉さん and 補佐.

姉さん is the subject of いーってならない (i.e., 補佐 is the subject of 一緒にいる)
姉さんが、一緒にいてもいーってならない人 (＝一緒にいても、姉さんがいーってならない人)

補佐 is the subject of いーってならない (i.e., 姉さん is the subject of 一緒にいる)
姉さんが一緒にいても、いーってならない人

Only the context can tell which is correct.