this could just be being 4 years old! Does she really know that much about the current situation that she's descended into anger and malaise? If so, that's your doing.
Perhaps you have only ever come across particularly stupid 4 year olds, but many children of that age notice things like not seeing their friends for months on end and not going to school.
For a 4 year old to be in lockdown is the same proportion of their life as if a 70 year old was locked down for 2 and half years.
It's not at all surprising that that would have an effect on their mood.
Blaming that on their parent is bit cunty.
You are a Dementor, and I demand my £10.