The last time they were in that room, Ripley gave Rose a chance. She knew that Rose had a tipping mentality and could easily spiral into an abyss of loathing, yet she wanted to help her. However, one of the most effective ways to help people like this is to give them a wake-up call, to hit them with the reality that they have been trying so hard to paint over. Ripley did this the first time they were there, harsh as she was, but it was necessary and not at all improper. Rose was the one who slapped the hand that was extended away. She couldn't accept the fact that she had never considered that Zeronis had his own opinion on who he wants to marry and that she had been dancing around in her own fantasy, oblivious to what was truly happening. The moment she began waking up from this dream, instead of fully waking herself up and finding herself, Rose chose to "intoxicate" herself back to slumber by getting rid of the one that was trying to wake her up. After this display, it has become clear that she is not stable at present and, albeit regrettably, Ripley had to send her to the monastery. It is at least better than the execution or assassination that awaited her at Zeronis's hands. Maybe she will attend their wedding as a nun in the future and be a changed person? Only time can tell.