It's totally normal! Anytime someone new (human or animal) joins the household there is a struggle to adjust.
In December our 3 young relatives came to live with us. They were 4, 3, and 15 months. I almost (well, I kinda did) cried everyday for the first few weeks. The energy in the house was so frenetic and I had to meet so many more demands that I thought we had made a HUGE mistake
We don't have children either, but 3 dogs. I was so exhausted that I just collapsed after they went to bed. The younger one had sleep issues, so I was running on empty half the time.
Believe it or not, it does get easier to handle. You really have to be patient with yourself and the process so you don't go crazy with all of these new expectations.
The thing that saved me was instituting a schedule that I really try to stick to. Meals and snacks are at set times for the older two so that I'm not CONSTANTLY fixing food. They also have an hour of quiet time each day so that I can recharge my batteries (this is a sanity-saver!) I think you'll start to feel better once she has started daycare.
You do adapt, but it takes time. I think I felt better after a month of having them. At three months it felt like they had always been here.