Very Very Long hair updo ughhh!!

I have a wedding updo on my client tomorrow and her hair goes to her knees . The bad thing is i've been wanting a practice shot with her at least 2x b4 the big day.. Well that never really happend I did one with her it was a disaster her hair was to dry, LONG, and it kept getting tangeled. I love doing updo's but how am I going to function doing this one tomorrow and no she wont cut her hair. I even tried putting her hair in a ponytail that didn't even hold good. I'm stressed I need help. I have a sample pic of how she wants her updo and yes its sooo easy to do I did it on medium length hair but never on hair that was down to the knees. Maybe a few of you might have some suggestions on how I can get this started and completed..

HELP!!!! Thanks