By "something", I only mean a kiss or something not so serious, but take it how you will.

Think of the time Renesmee took her first steps. She wanted Jacob to clap for her and make a big deal, so he did so without really trying or wanting to. She wanted him to, so he did without making a conscious decision to do so.

Jacob's fault, but only by imprinting. I can't help thinking that the crush might be caused by the fact that the imprinting forces him to be friends with her.

I don't see how it could possibly be Jacob's fault. He has no control over anything at all. He didn't CHOOSE to imprint on her, and he doesn't CHOOSE to be forced to do whatever Renesmee wants.

Yeah, didn't see "neither" as an option. I'm still blaming imprinting, though.

Do you mean when Renesmee's mental and physical age are similar to those of a 12-or-14-year-old girl or actually 12-14 years after she was born? I'm asking because according to the way half-vampires grow, when Renesmee is 12, her body will already be stuck at 17-ish.
I'm not saying I like the whole idea of imprinting (in fact, it makes me sick), but SMeyer was very clear: he must do as she pleases, which means she's ultimately responsible.

I mean mentally.

Thanks for the clarification. To me, it would make things even ickier, but she's the one making the choices and Jacob has to obey because he's imprinted on her.

I wouldnt blame either.

She's a child.

^ But Jacob wouldn't have a choice.

I would say that Jacob still had a choice to do whatever the question could imply, and since he's the adult, he has to be the responsible one.

According to the story, that wouldn't work.

I'm not saying that it wouldn't cause him pain to do so, but I think he would make the responsible decision.

I'm not even sure if he would be compelled in this scenario. Does her safety or well-being come into consideration as well as her happiness/obeying her every whim? What if she wanted to do something more physically dangerous, like cliff diving or riding a motorbike or even self-harm?

I know you gave the example of him automatically clapping when she first walked, but that was a slightly different scenario. There, he was giving her the reaction she wanted without focusing on his own fears of how rapidly she was developing. Being applauded wasn't actually harming her or risking her.