。
She is kind to whomever she invites.
Literal
She [topic-は] whom [object-を] invite [even-ても] is-kind.
誰を~ても ('no matter whom one X-es') is the universal-quantifier pattern using an interrogative + the concessive ~ても — same shape as 何を食べても ('whatever I eat'), どこへ行っても ('wherever I go'). The interrogative 誰 stops being a question word and becomes 'anyone / everyone' under the scope of ~ても. 招待する ('invite') is the standard formal verb for inviting, a step up from the more colloquial 呼ぶ.