Upvote:2
A British citizen doesn't need a passport to enter Ireland - you do however require valid photo ID that proves nationality and some sea and air carriers will only accept passports.
If you're planning on using a passport as proof of identity/nationality then it needs to be valid for at least the planned duration of the stay in Ireland:
Passport validity If youβre using a passport to enter Ireland, it should be valid for the proposed duration of your stay; you donβt need any additional period of validity on your passport beyond this.
So it would appear that you're going to need an alternative form of ID - e.g. Driver's License. And then it's going to be down to what forms the carrier will accept. If she needs a passport then the fastest way you can renew a Child passport is with the 1 week fast track service, as you can't do the same-day ones for Child renewals (only for adults).