Definitely get it checked out, but if it's not hurting or itchy then it's probably not herpes, especially for a first outbreak. I get cold sores on my mouth and they're definitely uncomfortable. I hear that outbreaks on the vulva are a bit painful. You say it looks like a pimple - it could very well be one. It could just be a clogged pore that swelled up, or a clogged sweat gland which are common on the genitals, especially in summer. I'm sure she's okay.