A party or reunion at someones house and the people are talking.
The party is full of people talking.
Only one party is mentioned, so 'the' is appropriate;  a party effectively consists of the people who attend it, and it appears that none of them is NOT talking, so it is fair to say that the party is FULL of people talking.
exists x6.(n_people(x6) & (exists e1 x1.(Actor(e1,x1) & v_talk(e1) & n_party(x1)) | exists e2 x2 x3 x4 x5.(Actor(e2,x2) & v_talk(e2) & at(x2,x3) & subset_of(x6,x3) & subset_of(x4,x3) & n_house(x4) & of(x4,x5) & n_someone(x5) & n_reunion(x2))))
exists e1 s1 x1 x2 x3.(n_party(x1) & of(s1,x2) & Actor(e1,x3) & v_talk(e1) & (x2 = x3) & n_people(x2) & Theme(s1,x1) & a_full(s1))