Learn Portuguese (Portugal): A aluna dedicada até insiste em ajudar os colegas. - The dedicated student even insists on helping her colleagues.

The word até is being used here as a focus adverb meaning 'even'. In Portuguese, focus adverbs are usually placed immediately before the word or phrase they emphasize. Since it is emphasizing the surprising action of insisting, it goes right before the verb insiste.

I thought até meant 'until'. How can I tell when it means 'even'?

You can usually tell from the context. When até acts as a preposition followed by a time or place, it means 'until' or 'as far as'. When it is placed before a verb, noun, or adjective to emphasize something unexpected, as it does here with insiste, it functions as an adverb meaning 'even'.

Why do we need the word em between insiste and ajudar?

The verb insistir requires the preposition em when you are stating what someone is insisting on. Just like in English where you say 'insists on helping' rather than 'insists helping', Portuguese requires insistir em followed by the infinitive of the next verb, which here is ajudar.

The word colegas ends in 'a' but has the masculine plural article os. Why is that?