In, On or At the Party: Qual é o certo?

Hello, guys!

I have questions concerning to the usage of prepositions followed by the noun phrase the party. Should I use in the party, on the party or at the party? Just to make it clear, this is not a specific party, the term here is used in its general way. Could anybody help me?

Thanks in advance!

NA.

She was at the party drinking a lot.

Como disse o Daniel, a preposição mais comum em relação a "party" é mesmo "at". Não aconselho o uso de "on"; "in" seria uma opção bem menos comum.