Is there any way I can convince her to allow me to watch her as part of our foreplay?

I am against pressuring anyone to do anything that they don’t want to do, so my first piece of advice to you is not to make a big deal about this because you may have to give up on this fantasy of yours entirely if she absolutely rejects it. That said,one tack that you might take is to ask her to pretend to masturbate for you. Be very careful to let her know that this is not something that you would want her to do regularly, but maybe from time to time, and see how she reacts. If her answer is still no, then you’ll just have to accept it.