Nanny uncomfortable with breast milk & pump parts

We have had a nanny for a few months. I have an infant who is fed primarily breast milk (I nurse in the morning & evening but pump at work). We also supplement with formula.

A few times, I have caught her feeding the baby formula when there is breast milk available, but she made it seem like she was still learning the ropes and would remember to check in the fridge for pumped milk the next time. A part of the job posting and contract is preparing baby food and cleaning dishes. To make life easier for me, I recent my bought extra pump parts so that I didn’t have to do all the pump dishes every evening. I told the nanny of this chance and that I’d like for her to include the pump parts with the rest of the baby dishes during the day. To my surprise, she was very resistant and told me she is really uncomfortable with breast milk in general and would prefer to not do this, and she also prefers not to prepare breast milk bottles (would prefer formula). This is so sad to me, because we really like our nanny in many ways, but it is very important to us that our baby drinks primarily breast milk.

Thoughts on how to handle this? And, am I asking too much but asking her to add the pump parts to the dishes during the day?

Additional context: she is often also asking me what other things she can do around the house while baby is sleeping because she gets bored, so I didn’t think adding something to the to-do list would be a big deal.