Point out that she might ask you, or expect you to do something she likes that you may not have a taste for doing... or for doing to her...

and is it her intention to think you're a bad dom if that happens? Obviously she'll not think that and you can ask her why it should be any different for you.

Secondly, point out that things that she can't do today, she may find herself craving or want to experiment with later... and you have all the patience necessary to wait until it happens.

Third, point out that her willingness to use her safeword (or whatever you two do to call a halt to play) allows you the freedom to rein freely and enjoy yourself. She won't want to take that away from you... and if you can't trust her to not feel guilty about it... how can you enjoy yourself the rest of the time.

Three different, overlapping concepts, that work for me.