Hey Diamond 
Don’t let it get to you. You know how desi culture can be…the hosts will often times push the guests to stay longer. You tell them you have a test to study for…they’ll brush it off as no big deal…you tell them you have to get up early to go to work…they’ll say koi baat nahin…tell em the kids are waiting for me at home…they’ll say it’s okay bachay theek hain…thori dair aur reh jaao. I’ve seen it so many times…you must have noticed it as well in various forms.
Some people are just not good at wording things…even though their intentions may be good. I think your friend’s brother meant to say that…you should have brought your daughter to the wedding…and that way you could have stayed longer and enjoyed the wedding with greater piece of mind because your daughter would be with you…and you won’t worry about how she’s doing at home. When he said “what’s so special about your daugther”…(again some people aren’t good with words)…and he could have meant that …in his opinion…your daughter could have handled a wedding with no problems…that the “special adjustment” (of leaving her at home) wasn’t necessary…because he personally felt…that she’d do just fine at the wedding. Of course, as the parent, you know your daughter better.
As far as your friend is concerned…she’s been with you since the past 14 years. Again not all friends are the same…and she just might not be skilled in matters of courtesy (delivering invitations personally, etc). Ho sakta hai k…since she feels really close to you…she becomes sort of relaxed with her manners. You know the whole “apno k saath” you loosen up with the formalities? If you feel that she doesn’t reciprocate when it comes to your needs (being there for you)…then don’t rush to be there for her all the time. It’s okay to maintain a distance sometimes.
The next time your friend asks you to sacrifice a huge amount of time to do something either for her…OR…with her…just calmly explain to her that while you enjoy her company…you still have to consider work and your daughter…and that these two responsibilities factor into your decisions.
****Is your friend’s brother FREQUENTLY involving himself in your matters??? If he usually stays away from you…and only acted this way during the wedding…then I’d let it go. It was a wedding…he was being hospitable…and encouraging you to stay longer. Now if he’s always involved in your affairs with your friend…that’s another issue. Could it be that he’s needed in those matters in some way? I don’t think it’s a good idea to tell your friend to tell her bro to get lost unless you manage to do it in a light-hearted jokey sort of way. Something like that is more than likely to cause offense.