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.
"There were four boys at the party" may imply that there were only four boys, but it doesn't necessarily and inescapably commit the speaker to that conclusion. Bear in mind, that this is the newspaper's wording. We don't necessarily know how she or her therapist actually put it at the time.
It's interesting that she didn't mention how many girls were at the party. The implication one might draw is that she was alone in the house with the four boys, but that's probably not going to be her story.
For the record, I think she probably told different stories at different times, and "four boys at the party, two in the room" is her way of reconciling the different versions. You can certainly treat it as yet another contradiction if she now says there were more than four boys at the party. I'm just saying that second-hand accounts without direct quotes can be deceptive.