Learn Polish: Była chora i wypiła gorącą herbatę.

Wypiła is the perfective (completed) version of the verb. It means she drank the tea completely and finished it. If we used the imperfective piła, it would mean she was in the process of drinking it or drank it regularly.

How do we know the subject is 'she' if there is no word for ona in the sentence?

In the Polish past tense, verbs change their endings based on gender. Both była (was) and wypiła (drank) end with an -a, which is the feminine past tense ending. The adjective chora (sick) also matches this feminine form.

Why do the words for hot tea change to gorącą herbatę instead of staying as gorąca herbata?

The tea is the direct object of the sentence because it is the thing being drunk. This means we must use the Accusative case. For feminine words, the basic noun ending -a changes to -ę (herbatę) and the adjective ending -a changes to -ą (gorącą).

I remember using a different case after the verb 'to be'. Why is chora in the basic Nominative case here?

You might be thinking of the Instrumental case, which is used after 'to be' when connecting a person to a noun (like saying 'She is a doctor'). However, when you use 'to be' with just an adjective describing a state, like chora (sick), you stick to the basic Nominative case.