I kinda already explained this through several threads..though can't find my posts, will cover it in my Analysis thread for Anakin. But I don't think innocent is the right word for Padme here, I mean she has fought in battle many times, she does care about her people and the Republic that is for sure. Really though, they spent a lot of time together alone while the movies don't really show this you pretty much have to take into account of what happens off screen of what you don't see(just like any other movie).
This more then likely was refreshing to Padme, as she got to actually KNOW someone rather then being hit on by snobbish senators or princes or whoever, never those wanting to get to actually know her.
As for her being manipulated...not entirely sure where that comes from, she was plotting with others(Bail Organa and Mon Mothma notably) against Palpatine.
To the Sand People thing, they are monsters. They aren't human in the sense that they actually care for anyone who they attack, I mean they train their youths to be killers, having them go out and torture beasts or humans(example Shmi). So them all being killed by Anakin, doesn't really make him a killer...he wasn't kill defenseless people he was killing monsters who go out, raid farms and carvans, kill/capture/torture the people and take their things.
She was manipulated in EP I, Palpatine used her to vote against Valorum. If we add the EU her election as queen was nothing but Palpatine's scheme, of course he underestimated her a bit.