On the other side of the coin, my Master once wanted us both to dominate another submissive. I tried to say that it was not my cup of tea, and that really I wondered why he was so adamant about it....

In the end it only caused me pain, the other sub was angry because I couldn't go through with it, and my Master was disappointed(not to mention causing some disagreement at home). Something like this should be a joint decision, if you value E, value her opinion.