OP... you're certainly NBU. Your friend's behaviour sounds extremely annoying, you should try harder to put a stop to it, don't just ignore her.
Snap to LadyOfTheFlowers, I happen to be in the same boat ie 3 boys, pregnant with 4th baby, 14 weeks today, and dreading all the comments that will no doubt come flooding once people get to know about the bump.
This pregnancy was a total surprise ( failed contraception ) so I wasn't ' trying for a girl' as no doubt I will hear lots in the nearest future.
My honest feelings re gender of this baby are that it would be nice to experience raising a girl but I would also love to have another boy as I adore my bunch of two teens and a three year old and found bringing up boys easy and fun (and I've found as teens they're even more fun and more loving as ever ! ).
I must say, though, that comments implying that girls are somewhat more desirable in general ( sadly, very prevailing in RL and on the net ) anger me more than the ones about having a mixed sex family.
The usual ' a son is a son until he meets a wife' or how daughters are closer to mums... yes , sometimes, but as a rule bull bull bull and once again bull, not my ( long ) life observance of immediate, extended family, friends, acquaintances etc