My youngest son is 18. I just showed him the picture and asked if he knew who she was. He didn't.
I then asked him how old he thought she was. He said "as young as 15, but maybe 17 or 18."
Now, a 17 or 18 year old girl is someone who he would consider dating. And she looks like she is the age to be dating. All your individual arguments aside, I think that spells trouble for an 11 year old girl and sends the wrong message as a daughter of the POTUS.
I asked my son, after I told him how old she was, if HE thought she was dressed inappropriately. He didn't know what I thought. He said "no." But when I talked about appropriteness for someone as young as 11 he still said no but kinda saw what I was talking about.
This is America where people can disagree about things. I've told you this to indicate that this particular case has some gray areas in it and I believe that most people looking at it would think that she was older than 11 and possibly above the age of consent. I my book that is inappropriate. Your mileage may vary.
So is it the t-shirt or the shorts? Should she wear a burka?