Your my will need to sign the form as she is the nominee, i think she has to go with you but i would double check by calling the DVLA as they can be a real pain in the arse, and its awful to get there then have to go away because somethings not right.
You need to inform the insurance company once you have changed the plate over, you will be given a letter by DVLA that shows you have changed plates so you dont have to stick new ones on in the car park, also dont forget to take your, MOT certificate if you need one and your tax disc as these both need to be changed, you will also need to take your log book with you.