Back to work/ freezer stash

Sarah
So I went back to work this week, M-F 8-5 for training. I prepared my mother-in-law as best as I could with notes and having her spend a day to see our usual routine, etc. I told her I will be pumping at work for the next days feeding, but Monday she would need to get in to my freezer stash... Well she did.. And fed her 25oz in 8.5 hours 😳, I only got to pump once and got 5oz so she would need to get into it again Tuesday.. Same thing, she gave her 5oz in one feeding and then gave her 18oz from my stash 😥. Tuesday I got 12oz pumping and thought "sweet she's set for Wednesday" nope!! She gave her all of that and 6oz from my stash.. So I counted what was left in my stash and immediately had a meltdown! It went from 125oz to 70oz in 3 days!! With my fresh milk included she was getting an average of 25oz in 8.5 hours!!! My body doesn't produce that much for her because when I'm with her she doesn't eat that much!!! I pumped another 12 Wednesday for her Thirsday feeding and flat out told her that's all she needs, don't give her more.. So now she thinks I'm starving my kid in order to keep my stash.. I told her she needs 1oz for every hour she hasn't eaten, not including the first hour since she should still be full..
 I also told her not to put all the fresh milk in a bottle, only put in what she needs to per the 1oz 1 hour rule because if there's more in there she will drink it whether she needs it or not.. Which my MIL stated she doesn't believe that... I even explained a breastfed baby doesn't eat like a formula fed baby in the sense they need more oz as they grow because my milk will change in consistency as she grows so she is still satisfied off a smaller amount than a formula baby... Because honestly, I'm not a friggin cow! It's all supply and demand! So if she doesn't demand 25oz in 8.5 hours from me, my body isn't going to produce it..
I'm sitting here like I know my baby best, I know what she needs better than anyone else, you are not the expert so abide by my wishes and requests!! 
I'm especially worried now because for the rest of my working time my schedule is extremely varied so I don't know 1. When I will get to pump 2. How I'm going to build my stash back up!
Let's just say I wasn't prepared for this issue to arise because I was confident my MIL would listen to me 😒