I was a bit
at the first page of responses, glad to see that subsequently people have posted who understood about bringing up children bilingual. Where I live there are a lot of families who are able to give their children the gift of being bi- or tri-lingual, and I have always envied them for being able to do so.
2 years of one language then increasing exposure to English via nursery sounds an ideal way to do it, leaves them plenty of time to be ready for school. Unlike where I grew up (non-UK), where on starting school age 5 or nearly 5, the population of my local school had barely 15% of children who knew any English at all. With hearing problems and severe speech delay I was considered so advantaged by being English speaking as to not warrant any support ...
From one of your posts, do I gather that there is a very large age gap between your older children and this little one? If so, I wonder what things may have changed at the nursery even with the same people in charge. The increasing prescription of an early years curriculum for instance - has this for example led to nursery staff having to focus somewhat more on documentation and rather less on responding to the children's needs? You could perhaps have an informal chat about "what has changed", and be sympathetic about paperwork etc, asking "do you find that makes it harder to ..." or something, and see how they respond. That, in addition to more specific discussion about how your daughter is actually finding her time at nursery, might help you in deciding how much to persevere with settling her into nursery now, vs finding a different environment for another year until she has more confidence for the nursery setting.
I hope you can find a way forward that you can feel comfortable with.