Mine still aren't perfect at sharing at 4 and nearly 3 but I'd say that Alexandra has got it over the last year or so big style, when it suits her. Same goes for Matthew really. Sometimes, they are happy to share, or at least say they are going to, and other times, its just "mine!!".
I used to think it was quite funny when Matthew used to get his way over and just take toys from older children when he was an older baby! The look on the kids' faces used to be priceless! You could see it was not done with any malice so unless he clonked someone on the head to get it (which he didn't), I would let it ride.
It's really hard when your friend is being touchy about it tho. I have a friend who kind of did that to me. She used to comment on Matthew's "behaviour" when he was just being an 18month old who was adjusting to being the elder, not only child. It used to bother me but she soon shut up when her own child got to that age and she found out what it was like to have a child of that age in the house!
kateab