That is a bit hard indeed and there are 2 stages where you might have gotten stuck, but the costume is required in both scenes and the devil ending needs to be unlocked for the 3-way.
I'll presume you were able to get the costume already ;)
You will have to listen to whole Angelica's backstory and then if you'd have already given her the costume on the last one, you will have a choice to let her know that you don't think she is a "sweet precious girl" ;)
I hope that helps.