Lol Slim, didn't look at the original date did you? ;P
As to the zombie master...for a 5'6 woman that 18" is too big for a mountain bike. Depending on your proportions you would probably be more in the 15-16" area.
Properly maintained hydraulic discs are the best kind for MTB. The rear disc could be an add on yes.
Your link is dead btw.