This one is lacking many appropriate english translations. It's very frustrating to have to work to memorize the accepted translation because the duolingo approved one sounds extremely unnatural to a native speaker.
No. In+acc is a direction. She has the flowers and puts them into the room. In+dat is a location. She already is in the room, and puts them down right there (you would have to say "sie stellt die Blumen in dem Zimmer ab" in this case.)