Never leave the child in isolated room. Parents/mother must sleep by the side of child. It is one of the ancestral practices which is erased due to modernization. Mother's touch gives security and confidence to child. Make it a practice, things will improve.

Your child might be too tired. It's important for them to have structure. It might be that she is not resting enough during the day. Children can also resent other siblings and the attention being diverted to other things that we might be occupied with. If there are other siblings I would probably suggest to dedicate some time for her alone on a daily basis. Being a parent is by far the hardest job and the most rewarding. Children need us to have unconditional love for them. It's hard to communicate with someone that is already upset. I would suggest to hold her and kiss her and to assure her how much you love her first and then once she's calm, you can talk to her. Anyway I hope this helps :)