Please use caution when looking for a new bird, since the UK area in a chicken lockdown. My state went through that last year. I heard a lot of existing flocks for that year died or euthanized cause the disease was spreading so fast.
Watch over her for 30 minutes. Write down everything you see, be descriptive on every symptoms. This includes how she is eating, drinking, or not, her routine habit, convulsions, posturing, anything that looks off. Take notes. Then post your finding here in detail.