It sounds like the two of you are on the right track to gradual, natural weaning, and it also sounds as though your daughter is thriving on whatever mix of food and milk you are giving her, since she is gaining weight appropriately. So you must be doing things right!
In terms of her nutrition, how much milk (yours or other) she needs depends largely upon what else she is eating. I know that starting at 6 months it's a good idea to start giving them some iron- fortified rice cereal (mixed with breast milk), and to continue adding other foods gradually to their diet, leading up to other sources of protein and calcium when they reach 1 year. Before she weans entirely, you'll want to make sure your daughter is getting protein and calcium and other nutrients from food sources (like tofu, broccoli, milk, etc). I remember using a really helpful book called "Mommy Made", kind of a cookbook and nutritional guide for children 0-4. It includes all sorts of guidelines and suggestions about when to add certain foods to a child's diet, which foods have which necessary nutrients, how much, how to prepare, etc. I found it really helpful to have this (or some other) source for making sure my child got sufficient nutrition, particularly when she was no longer getting it from me.
I've found that doctors and pediatricians are not very knowledgeable about the specifics of nutrition (they either tell you to go to a nutritionist, suggest formula, or issue blanket vague statements like "give her calcium" that aren't specific or useful). However, there are a lot of good books and nutritionists out there who know a lot, and they are worth consulting if you are in doubt. Keep in mind, however, that your child is growing and gaining well, so you probably don't want to drastically alter whatever you are doing in terms of feeding her.
In the meantime, just keep doing what you are doing, which sounds just right: nursing her 3 times a day and giving the frozen breast milk. The golden rule as I recall for weaning is "Don't offer, Don't refuse" so I'd say continue on with your/her routine for as long as she is content. She'll start to ignore or "forget" certain feedings, and it will happen naturally I bet. So long as she is eating food regularly throughout the day, she'll be fine.
Good luck!