Try this--with her dominant hand, have her put two fingers to her neck, like you do when you are taking your pulse. In this order (progression of difficulty), have her:
1-- Have her count her pulse out loud (1,2,3,4,etc., don't repeat these numbers, count to 100), I think this is better than a rhythm from an external source, this is internal. I think that it's important to start with the very easist thing.
2--Have her now add the foot that is on the SAME SIDE, (still counting out loud). She has to do her own pulse (it has to come from within) rather than yours.
3--Do #1 & #2 again but with the non-dominant hand and foot.
4--Go back and take pulse with non-dominant hand, and while counting out loud, her dominant hand will tap out the rhythm that she feels with her other hand. Up until now, there has been no way for you to check up on her, without her feeling dorky

, and you've been wanting her to avoid that, right?!
5--Now, have her take YOUR pulse (probably from your wrist, so that she doesn't feel dorky!

) Go through all the steps. Since it's YOUR pulse this time, you can check up on her before she goes on to...
6--Now, she goes back to taking HER OWN pulse with non-dominant hand, her dominant hand will continually tap out middle C, tapping to the pulse she feels with other hand.
7-Same as #6, but play c,d,e,f,g, and back down. Over and over.
8--Same thing,but SAY la, la, la with each note (or her boyfriend's first name, but it has to have one syllable!

)
9--This might be tricky! Do #6, #7, & #8 but have her feel YOUR pulse instead. Now you can check up on her!
Keep progressing on, but by now, you can make up the steps. Always keep in mind, to have her feel it from within first, before moving to an external source (taking your pulse).
Try these first. If you need more ideas, please post again! I hope this makes sense, because I'm tired and not thinking clearly now. Have fun!

Peace,
Janice