lol you can get a certified copy of the original entry in the birth register, the original full copy certificate is the one you paid for when she was born but have now lost.
The links you have been giben by old geezer and or maydup are correct, ignore any conspiracy theories,
The cost will be £9.50 and it tales 7-10 days but if you can get into the office where you originally registered her you can get a copy then and there, also, the reference you need is shown on the short copy certificate that was free at the time of registration.