First of all, you are doing a great job of providing your child with the best nutrition there is. Pumping is a big commitment and you have a long work day. She is lucky that you are working so hard to keep up your milk supply for her and provide her with breastmilk.
It is normal for babies who take bottles to wean themselves earlier than babies who've not had the option. Although nursing at the breast is important for jaw development, it is also takes more effort and smart babies figure that out. As babies get older, they are also more easily distracted. Some babies do better at night and in a dark and quiet place with fewer distractions. Some babies go on nursing strikes because of an ear infection (upright nursing would feel better) or teething or other problem that could pass. You will need to add pumping sessions to cover the missed feedings to keep up your milk supply. Your body is able to respond to increased and decreased demand for milk within a day or two. For example, sometimes older babies get sick and start nursing around the clock when they can't take in solids and the nursing mom's milk supply responds. It takes a day or two after the illness to ramp back down. So you have a lot of control over that.
You can keep trying to nurse by keeping things really relaxed (it must feel really frustrating when she pushes away) and make sure she has plenty of cuddling time. Some babies like to nurse in a tub if you take a bath together or even a shower or laying down at naptime or bedtime or in the night if she wakes up. Often working moms can skip bottles on the weekend and just nurse. Babies get used to that routine.
Have you changed soaps or fragrance or even laundry detergent? Some babies are very senstitive to fragrance.
Hang in there! And remember that you are doing a great job no matter whether she has pumped breastmilk in a bottle or takes it straight from the source.
K.