Toddlers eat very erratically, so be glad you are nursing.
My dd is 2, and we just watched her for signs of readiness for solids. She ate token bits of our food--whatever we thought appropriate and healthy for ages, and she didn't start asking for meals until 18 mo or so. At times, she still hardly eats anything, and at times, she eats a ton.
As long as you're offering her healthy foods and she's healthy, she's fine nursing a lot and eating a little. You can try offering solids first if you want, but I wouldn't force it. We're trying not to make food an issue of any kind around here. Prepare things that are easy, so you don't feel bad if she doesn't eat them. And watch out for nursing after fod, because food left in the mouth can cause abrasions to the nipple.
Many breastfed toddlers experience a growth plateau around 1 or 18 mo. They may even stop gaining weight at all for a while and really slim down. Don't worry if this happens to your dd, as long as she is healthy and has appropriate energy.
If you think she's nursing a lot out of thirst, you might offer her a cup of water (not juice--empty calories) first, especially in hot weather.
Many kids delay solids because they have allergies to foods. Avoid high;y allergenic foods, if you think this is a possibility. But 12 mo. is not late to be taking solids for a bf baby.
Try Sears' Family Nutrition Book if you haven't already.