We just went yesterday. While I don't recall there being anything particularly inappropriate for her age (although she might get a little freaked out when the Red Skull reveals himself), there also is nothing that is particularly age appropriate either, so I would not suggest you take her. She will probably be quite bored. The movie is mostly set in WWII era and there are plenty of historical references that she won't understand (like who Hitler is and the selling of war bonds, etc) and also characters that relate to other Marvel super heros that she may not be familiar with (ex: Howard Stark, who is Tony Stark's father...Tony Stark being IronMan).
All the humor is subtle (mutterings or brash comments made by a military colonel--TommyLee Jones) and she won't get it.
It was a wonderful movie. Just get a sitter and go without your 5 yr old. Our daughter is 10, and she enjoyed it. But at 7, I don't think she would have, let alone at 5.