Complex sentence: Carrie is heartbroken and some months later she runs into Big at a party in the Hamptons; he is accompanied by his 20-something year old girlfriend, Natasha, whom he met in Paris.
Split into simpler sentences: Carrie is heartbroken and some months later runs into Big at a party in the Hamptons. He is accompanied by his 20-something year old girlfriend, Natasha, whom he met in Paris.