5 year old anxiety

[Everestisthebest]

My 5 year old daughter has been experiencing some bad anxiety recently. Example my younger daughter stuck something up her nose and my 5 year old got so freaked out, was crying in hysterics whereas my 3 year old was unphased. The other day my 3 year old was hiding somewhere in the house, we knew she was hiding I saw her run upstairs but my 5 year old completely panicked was crying and couldn't be calmed down. She gets really upset if she's putting on her clothes and can't get her arm out or it gets stuck over her head. I'm wondering if anyone has any advice on how to help her with this? Don't like to see her so panicked so easily..

How recently? Just wondering if it could be partly related to school holidays/ change in routine?
Both examples relate to her younger sibling. Does she take her big sister role too seriously?
If so she may need the family hierarchy explaining explicitly that it’s Mummy’s job to look after sister, nice that she cares etc but she can be a good sister by playing, sharing books and toys etc.
Could the clothes difficulty be sensory? Worth observing and exploring.
If it continues I’d explore a Worry Monster, books about worries etc and speak to her teacher in September if it persists.