Learn Portuguese (Portugal): Ela vai visitar-nos.

In European Portuguese, direct object pronouns like nos (us) are usually attached to the end of the verb with a hyphen. Because visitar is in its basic dictionary form (the infinitive), the pronoun just tags along at the very end.

Can I put nos before the verb instead, like Ela nos vai visitar?

In Portugal, it is much more common and naturally correct to attach the pronoun to the end of the main verb in a sentence like this. Standard European Portuguese strongly prefers visitar-nos, even though you might hear the pronoun placed before the verb in Brazilian Portuguese.

Does nos change if the group of people being visited is all female?

No! The pronoun nos means 'us' and it stays exactly the same whether the group is all men, all women, or a mix. Unlike o and a (him/her/it), the pronoun nos does not change based on gender.

Why is the main verb visitar not conjugated?

This sentence uses the verb ir (to go) to talk about future plans. The structure is ir plus the infinitive (the unconjugated dictionary form of the main verb). Here, vai is the conjugated part matching Ela, so visitar simply stays in its basic form.