Re: Not a "good pumper". Need advice.
My main tips for making supplementation work were included above. Nothing too complicated, I just nursed on demand when I was there, especially at night (which I think is what really kept my supply up in the early months especially). While I nursed, I never gave a bottle myself (except this one time we were stuck in traffic and I hadn't learned the fine art of nursing a baby in a car seat) so they would associate me only with nursing. I continued to pump regularly- with my daughter I did 3 times a day until she was about 9 mos old, then I dropped down to twice a day until she was about 13 mos and stopped taking bottles so I pump weaned. She continued to nurse for another year after that until my supply dried up when I was pregnant with my son.
As far as your caregiver (your mom I think you said?) giving formula bottles, the teachers at my daughter's school preferred to save the breast milk bottles for nap time because she slept better that way. It's never a good idea to mix them, so if there's not enough breast milk for a full feeding give the breast milk first and then the formula. Stay vigilant about overfeeding (you'll have to look up amounts of formula to give at each age) so your LO doesn't get used to that over-stuffed feeling. And try and make sure she doesn't give bottles too close to pick up time so LO will eat as soon as you get to her.
“We are not put on earth for ourselves, but are placed here for each other. If you are there always for others, then in time of need, someone will be there for you.”