Have you spoken to her about this? Depending on what the medication is the doctor might be able to change the dosage or switch to a different medication. I don’t think your girlfriend is doing this for shucks and giggles, and she needs to know that this medication is affecting you, too.

Your social interaction is just with your dogs? Are you bragging? Are you trying to make us envious -- we who still have to put up with humans?

Take her to therapy. I don't mean that in an unkind way.

You can help her (and your relationship by (1) convincing her to make an appointment with the doctor who prescribed the medication, and (2) writing down the side effects that you've observed, and making sure she takes the list with her to her appointment. When patients are dealing with medication that alters their mood and cognitive functioning, they aren't always reliable narrators of how they've been doing, and doctors know this, so they may discount what the patient tells them as being exaggerations or half-truths. A simple, non-judgmental list of what someone else has observed her would probably be valuable for the doctor. And things aren't going to improve unless she works on this with her doctor; she may be so apathetic and unmotivated that she doesn't even want to want sex, but that's the medication, not who she really is-- so if she's not eager to go, make it easier on her by driving her or whatever. Good luck!