Down Syndrome. Am i way out of line here?

I'm a little curious after i got into a mive argument with and old friend. The thing is her and her partner have two little boys. One is 6 and the other is just toddling. The elder son has down syndrome which is sad but he is such a happy young chap full of smiles whenever i see him. The thing is ever since she descoverd that he has down syndrome she seems to be obsessed with it. I know she has every right to feel concerned for his well being but for example on her facebook it will just be stat after stat, day after day of diatribes preaching how children with down syndrome deserve acceptance. I even helped her out with a charity a while back. I'm aware it's a part of his life but he's so much more than a child with down's syndrome. My friend seems to hung up on his handicap. The **** really hit the fan when we were out at starbucks (it was just me and her). And i went to reach for the milk and i knocked it clean off the table. Laughing and reaching for some tissues i said "gah im such a retard". She just went absolutely crazy at me with "DONT YOU USE THAT WORD I HATE THAT ******* WORD!". I just stared at her in disbelief. Then i got up and left. I feel like an . I just wish i knew how to articulate how she's behaving.