5 year old and newborn

I have a one week old boy and a 5 year old daughter. She started kindergarten in September but it was a very rocky start as she got a huge cold that kept her home for at least a month. Needless to say, we didn’t establish a great school routine before baby arrived. Nevertheless she is doing well adjusting to school and her teacher has only positives to report. However with baby here now, she goes in and out of jealousy and once home from school, is majorly demanding and whiny. I want to be attentive to her as much as possible but obviously it’s difficult with breastfeeding and baby at night. She is used to having all my attention and now must share it. She loves her brother but she is showing little behaviours that I’m worried about. Not as patient, cheating in games when she didn’t used to, crying a lot, etc. I notice it’s mostly at the end of a school day and I get that many kids stuggle at that age with regulating their emotions after a long day at school, but I find myself so worried and stressed about how to help her when I’m so busy with baby. Her dad is only partly in the picture and my boyfriend helps a lot but I’m really her go-to person which is hard these days. Today she woke up at 4:00 am! For no reason other than I think just feeling unsettled and now she has to do a whole day of school. Before I would have picked her up mid day so she could rest at home but I find with baby here it’s so hard to have her home.

Any advice?? I am a very gentle parenting type person who is very responsive to her emotions and we are extremely close. I struggle sending her to school knowing she isn’t 100%