At this point, I would say she should be nursing atleast 4 times a day. Breakfast, Lunch, Dinner, bedtime and maybe a snack in there somewhere. Are you nursing her before she eats the baby food? If not, I would recommend that. Try to be patient with her. If you are stressed, she will react to that. Also, she may be distracted by others in the room. When my babies were about 7 months of age, they would rather see what was going on than eat. I just had to keep directing them to my breast. It also would help, if I could send my other children to their room while I was nursing. That way, we could have "quiet time". The babies would do much better then. Another thing is that I would have to turn off the TV sometimes or stop reading a book while I was nursing.
Hang in there. You are doing a great job by nursing her this long. If you don't want to give her formula, then don't. Be patient and continue to offer the breast. She will nurse as much as she needs. Just continue to offer. I nursed 4 children (3 of them until they were 14mo. old) and yes, I struggled with each one of them at times to continue to nurse. But, I was determined not to have to give them formula. You can too.
Also, don't be afraid to call the La Leche League. They are big on breastfeeding. I called them once when my baby wouldn't nurse, and they gave me really good advice.
Hope this helps.