Hi - You're bound to be nervous - we all get like that especially with new clients and weddings! if it helps bring along your beauty book you studied in college to check face shape/eye shape etc and the best makeup to do for her, above all make sure the foundation is right for her skin tone, after that its all about what colour theme they're having at the wedding..... have fun while doing the trial, mess about with different colour themes for her, when my sis got married she was wearing ivory and we were in red and it was winter time so i did natural eyes(golds /browns, brown eyeliner for a softer look) nice bronzer/ blusher for the wintery look and so she wouldn't look so pale and a lovely reddish lipstick to brighten up the makeup...hope this helps
Lisa