Is my girlfriend cheating on me?

Hi, I'm a 28 year old guy and I've been with my girlfriend for about 8 months (writing this in August). The other day I asked her if I could borrow her laptop and whilst I was using it I got nosy and looked into her facebook messages (I realise I shouldn't have!). I've found out that she's been messaging her ex-boyfriend since April, asking things like whether she could meet up with him again for a coffee, or if he's around on a certain day etc. They met at uni and were together for 4 years but he dumped her because he was (and still is) suffering from depression.

I don't know what to make of it. Is she simply just being caring and checking to see how he is? or does she still have feelings for him? I'd be fine with it if he was just a male friend but the difference is that they were a couple. She'd left him more messages than he'd replied to and it almost looks as though she is still pursuing him and if he wanted her back I feel like she'd dump me for him... The language of the messages is what I would probably call friend territory, although in a couple of them, they'd both left xx after and in one of them, he said that he missed her and hoped to see her again. In all there were about 15 messages since April, about 10 of them from my girlfriend.

What should I do? Should I ignore it and assume that she's just wanting to see how he is from a friend perspective? Do I wait a while and see if she continues to message him, actually meets him and then confront her? Or do I confront her now and ask her to explain why she's still messaging and wanting to see a guy she's supposedly broken up with? We've been together 8 months and we get on great, I don't want to ruin our relationship or make it awkward when she may genuinely be innocent..

Please help!

Does she display in her facebook page that her and you are boyfriend/girlfriend?
Has she shown you in action that she is acting shady or less attentive to you then she once was?
What made you invade her privacy in the first place? Is it your insecurity trust issues or did she give you reason to check due to being shady?
Is he still a facebook friend? If he is, perhaps you could ask if she is still in touch with him and if she lies to you, then you have a decision to make.

One thing for sure is, if you are going to snoop then you better be prepared to talk to the person you are snooping on about what it is you've discovered because if you're too afraid to do that, then what is the point in snooping.