What does Bueno mean?

"Bueno, let's just chill at my place tonight," she suggested.

Dutch student slang. This is a Dutch word. You will hear it a lot at Dutch universities, student associations and in student houses.

Students drop it into Dutch sentences to say something is fine or settled. Usually without speaking any more Spanish than that. It is part of a little family of borrowed words, like vino and tranquilo. Also read what valid means.