I am glad you changed the first point; because if I was reading it, I would see "calendar days" and think "Sweet, 14 days. Of course, I will only use them on M-F". So I see why you needed to do that. But from her standpoint, she may feel like you are taking away vacation days she thought she had. Certainly, you are entitled to sick days, etc. And I think it's pretty generous that you deduct any money. But again; it isn't what she agreed to, originally.
Depending on how long they have been with you, I can see that she may not like changes being made, especially if they are in your favor.
I have a clause in the handbook that says that changes can be made to the contract, given 30 days notice to the client. The fact is, sometimes we need to do this!!
I don't know that I would play the fact that you are giving her care outside of your normal hours. That was, and still is, your decision. It's not fair to agree to it, and then be upset about it.
I had a provider once when my boys were little, that looked after them p/t. The reason we chose her was she agreed to Saturday care. 3 Saturdays in a row, she called me "sick" in the morning. Finally, I asked her if there was an issue and she said she had changed her mind about the weekend care. I was PISSED.
So, essentially, I can see both sides of the story. If she has been around for 4-6 months or less, I think I can understand why she is mad. You DO have the right to make changes to your business, though. The next time she texts you, text her back and say "I am under the impression that you are not happy with the recent contract changes. I would feel more comfortable discussing this either on the phone, or in person. Can we chat for a few minutes tomorrow?" Texting is a very passive-aggressive way of communicating, and while it can be good for some things, others need to be directly discussed!