Girlfriend added guy who hit on her on facebook?

[Joshua]

Essentially my girlfriend of 2 years and her mum were out, a guy who was around 28? Came and hit on her (She's 17) and she tells me she brushed it off and laughed. I asked for more detail but she was shady, about a week after (today) I went on facebook and I saw she had added some guy, not unusual but his only mutual friend to me was my girlfriend... She had told me the guy had curly hair and was posh; after looking at a couple of pics I was pretty damn sure it was the guy so I text her 'Who's *********? Haha' and she said 'Oh I think I know him through my sisters, not sure' my response was 'Oh I thought he looked like that guy who hit on you, and he's found you' and then she admitted it was him; I freaked out as you can imagine and she just kept saying: Oh this is what I mean after 2 years you still don't trust me? - bridges have been built and there is peace now, she told me he knew her name and searched her up, they had not messaged and he didn't have her number?

So my question(s) are:

Was I within my rights to freak out?
What's your opinion on what she did?
What would you have done?
Any extra info would be great

Cheers ladies and gents!

And yes it does have a link to my insecurities before that pops up!

[Chelsea]

I think you should start to trust your girlfriend a bit more. An add on Facebook isn't a big deal as long as they're not messaging. She might feel like she had to lie about how she knew him because she knows you don't trust her? Unless this is happening a lot then i think it is just a little bit of an over reaction, but at least it shows you care about your relationship

[Dee]

first of all i think you did good because why would she be friends with a GUY that HIT her
2 in my opinion i think something else is going on because it that was me and he had hit me i woukd bragged him by the b@ll$ and never speak to him what kinda of "man" hits a girl
and i would ot not accepted his request and blocked him
Good Luck

[Marco]

It's only Facebook, as long as he doesn't have her street address she's fine, people add others on Facebook all the time! In my experience, half their friends list is people they don't know...