Regardless of what other people think, you will probably be breastfeeding your daughter for quite some time. It is still nutritious. Nothing magical happens to your milk at 1 year. Is your child malnourished? If your child does not appear malnourished to all these people around you, then it is none of their business what you are feeding her. You shouldn’t have to do all this “explaining”. I have many friends with younger kids, and I have no idea of what their kids eat – I guess I never really see them eat. Do you have to explain all the time because your 1 year-old is nursing in public all the time? If this is case, then maybe it would be wise to start setting limits with your daughter, such as “we only do nummies at home”. This worked well for our kids at this age. Let’s face it, it’s no fun to get all those disapproving stares at the mall.
Regarding scientific data, I have a feeling this won’t help you convince anyone of anything, but you could just tell them that the American Academy of Pediatrics new recommendation is this: “It is recommended that breastfeeding continue for at least 12 months, and thereafter for as long as mutually desired”. A “google” search will get you the full recommendations if you want to read them for yourself.