If she is available and your child is eligible and its you who have decided to suspend the contract, then I'm afraid she is in the right.
Is there a force majeure clause in the contract?
Who served who notice that the service was not needed or no longer available ?
Yes this is a small claim fast track.
I'm not convinced you'll win
My child is no longer eligible though, he was but is now not, this was due to the ever evolving world of covid. My wife was initially classed as key worker, the government after a week then changed stipulations regarding Mots etc which then meant my wife was not classed as key worker, and so has been put on furlough by her bosses.
The child minder told us the service was no longer to be offered last night