Maybe work with her empathy, and let her know how much you have loved feeding her but how it also uses up lots of energy and makes you tired making milk for 2 people. If you had more energy then you could do other things with her like x,y,z

My DD will now accept if i am too tired to breastfeed her. I have to introduce an idea, and then talk about it a few times before she understands, or accepts it...but i know that she is thinkig through the idea herself in between us talking about it cos she will bring up a new thought on in the next conversation.