I have faced the same sort of thing with a woman before. While you are gone working to support her happy little azz, she is at home chatting it up on messenger.
Here is the bst advice yet. This is if you still wanna be sure she is not just bored etc. It also helps with the kicking out process.
Got to a place like cnet.com Download a keylogger. DO not let her see you do this. Install it on the computer. what a keylogger basically is, is a invisible computer spy. It logs every keystroke. You and you alone can make it "visible" and you can read every freaking word she has typed and print it out too.
What i did was ask the biotch to look me in the eye, and tell me honestly if she was meeting any guys and flirting, meeting for sex etc. Of course she will look you straight in the eye, and say nope, they are just friends. i get bored. I need something to do. Ask her to repaeat that she is being fauthful, just so you heard it right. She will.
So you install the keylogger give it about 2 days. come home get her away some how, and start looking. No doubt you'll see all sorts of shyt. She might even be discussing meeting with a guy AGAIN, or how nice his dyck is etc etc. Print this all out. Call her in the room. Sit her down. ask her the same question you asked her again previously. She will no doubt lie to you again, and say, geez, just internet buddys don't be so jealous, lighten up etc. Thats when you throw the stack of shyt you printed out on her lap. Say then what the fvck is this shyt? Tell her right then and there, look bytch, you lied. Not only did you lie, but you lied and looked me in the eye several times. No more free ride. get the fvck out.!!!!
When I did this, it worked great. A great side effect, was that they always think they are so smart right? So she will have been outsmarted too, which will get to her like crazy. Its just a great way to show them, you take no shyt but you were trying to be fair. If in doing this, you find out that she is telling the truth, and is talking to a bunch of girls etc, then you need to find her something more constructive to do. Its not good to let her sponge off of you and do absolutely nothing to contribute. get her used to getting up early. Assign her daily things you want done. change your internet service, and don't let her have the password to log on. That will fix that, if you plan to keep her around. I know some guys will just say next her right away, and why go thru all of the stuff I describe here, and that is up to you. I did it this way, cuz i did like the woman, and before i booted her azz, wanted the irrevocable satisfaction of having all the proof, so that I couldn't be misconstrued as closeminded, or mean or "imagining little scenarios that weren't true. Do you know the tv show cheaters? They film people cheating on each other, then confront them with the evidence. Funny how they suddenly, have no choice but to tell the truth. Makes handling it so much easier, and they know you know, and they can't play the benefit of the doubt game on ya. anyway, its a thought. If you don't wanna go this route, then just kick her out....i jut wanted you to know about the keylogger..its great for catching liars in a lie!