My grandmothers sister was a nurse in the early 1900's. she was born 1885. I have a couple of photos of her in uniform and an envelope with "Nurse Brace" written on the outside and a dark blue and red chevron fabric badge inside.
She lived near Newport here in Wales and worked with the local doctor.

How can I find out where she might have trained?

http://www.rcn.org.uk/development/rcn_archives is probably the best place to start.

Thanks for that - will try today.