I noticed that too.
It sounds like she told two stories that conflicted and tried to smooth over the differences later.
But I don't believe she's on record as saying there were only four boys at the party, just that those four boys were the one's she knew were at the party.
Her clarification strongly implies strongly that there were four only at party. Therapist said “four boys,” she said two - she says therapist misundertood - there were four at party, two in room.