Is it ok to mix milk from the left and the right breasts in one bottle?

Yes. Same milk, different dispensers.

The breast milk that a woman's body produces is going to be the same milk regardless of which breast it comes from. If a woman is pumping, she can pump one or both breasts and store the milk in the refrigerator. If her goal is to pump 4 ounces and she only gets 2, she can even add pumped milk to the bottle containing milk from a previous pumping. Proper breast milk handling and storage has a variety of recommendations depending on what source you get your information from. Generally, pumped breast milk can stay in the refrigerator for several days, around 3-7 days depending on the source. Breast milk can also be frozen for varying lengths of time. If it is the refrigerator freezer with a separate door from the refrigerator it can last about 3-6 months. Milk in a deep freezer can be good for 6-12 months. It is perfectly fine to mix expressed breast milk as long as it is being properly handled and stored.

of course, their is absolutely no difference. You can also pump breast milk into little baggies and freeze it.

just wanted to throw in another yes......i did it all the time......i had a single electric pump and that i would switch back and forth between breasts

yes my wife did all the time it's all coming from the same place.

Totally okay.