YOu shouldn't let that annoy you. You have quite a few pets already, and the suggestion that you be happy that she allowed that many is a good one. A negative emotion will do no good. Think of it as you saving money up until you move out and can get the critters you REALLY want but can't afford right now.
Some people simply think that you need to devote all of your time to an animal, even when you only need to give them a small amount. A dog needs tons of attention, but a lot of reptiles are healthier and happier with less.. much less. Especially less hands-on time. But someone more focused on furry pets won't understand that.
Just nod and smile and care for what you have until you get to move out.
Respecting our elder's wishes is a good thing. She's housing you, and your pets, being a bit more grateful about it would make you be more positive.
Wolfy