Just to voice my opinion:
1) 28 months is NOT too late! If your friends and family are giving you a hard time, just ignore it. My 5 year old neice couldn't poop in the potty without huge trauma! Anyway, it sounds like your DD is right on track because,
2) It's very, very common for kids to be comfortable peeing in the potty, but not pooping.
Kids don't really understand the concept of elimination. To them, poop is part of their bodies and many have a really hard time understanding why it's something to get rid of. In addition to flushing her poop from her diapers, you might want to consider involving her in the process. We make kind of a deal out of it by waving saying "Bye-bye poop!" and then letting DS (26 mos.) flush the toilet. (We do it w/ pee, too.)
Also, if they are told that it's yucky, dirty, bad or something equally negative, they may develop a fear of it and not want to poop. If she seems interested in touching it or anything like that, try telling her that it's kind of stinky and you don't want to get it on the toys/furniture/whatever and that's why poop isn't something we touch. Be sure not to scold her for it.
Finally, consider getting a copy of "Everyone Poops" if you don't already have it. It's a great kid's book with nice artwork showing a huge variety of animals (humans included) and their various poops. It's actually pretty cute and funny.
ex-Californian, making my way on the East Coast with DS (10), DS (6) and WAHDH. Former extended BF'er, co-sleeper, and baby-wearer. Remembering how to garden.