As-salaamu `alaykum warahmatullaah
While I don't feel the mixed emotions people are speaking of and simply see it as a 'happy' photo for lack of better words, saying that the sisters post won't help in 'turning to islam' and stuff like this causes you to leave is a bit far-fetched on your part (in my opinion). It's just a photo and we are all entitled to our opinions, especially with things as trivial as this. Mine, yours or anyone else's opinion on this matter doesn't really warrant much to life, and I'm pretty sure I can show this picture to 1000s of non-Muslims who are likely to feel very similar emotions to what some people have expressed.
Many renown non-Muslim thinkers and politicians too feel sorry for soldiers for the same reasons that we might, but since this isn't a political discussion I won't elaborate here.
And for the sake of clarification, considering some past posts of yours I've noted, in this case it is not that a Muslim girl is giving a flower to a non-Muslim that is a problem. The discomfort stems from the pretty obvious connotation or fact rather, that the oppressed is gifting her oppressor (not in a literal sense). Had this photo shown a Vietnamese girl doing the same act in the 60s it would've replicated the same emotions. Such emotions wouldn't have had an effect on one's perception on religion, and nor should this.
Take care,