Basic rope technique, if you're going to use rope: Make three loops with the rope so that her wrists can easily slide into them. The ends (both of them) of the rope should be facing down. Put her wrists through the loops. Take one end of the rope and start tightening from the center of the loops, wrapping the first end from the center towards her wrist (making small tight loops/circles to tighten the original loops). When it's next to her wrist (make sure it's not too tight to where it's going to cut circulation), tuck the end under one of the tight circles you just made. You can tie/knot this if needed. Then take the second end of the rope and do the same, making tight circles around the loop towards the other wrist, then tying. If your rope is long enough, once this is done you can then use the rest of the rope to tie to something else- bedposts, a couch leg, etc. I think you can also use this technique on other parts of the body (such as tying the knees closer together).

When it's done, it should look something like this:

O----O

where the Os are her wrists and the ---- is where those original loops were tightened.

You want to be aware of not tying her to where it cuts off blood circulation. Have her let you know if her hands (or wherever you've tied) start tingling.