Dear Ibby, All my GF wants to do is fuck. Sometimes, I just want to talk. What gives?
What gives is that you are the luckiest man on Earth and if you don't appreciate her uniquely high libido for all it's worth, she'll find someone else that does.
Especially since your so-called problem has a simple solution: fuck first, talk later.
Or talk first, fuck later.
Either way, the root of your question is that you're both looking for connection — you're just doing so in two different ways. For her, it's physical. For you, it's emotional. However, your need to communicate and her need to bone you aren't mutually exclusive: it's relatively easy for both of you to get the kind of connection you want in the same night. Hell, same hour! Same minute, depending on your dick!
Also, guess what? You can even talk while you're fucking ... assuming the topic of conversation doesn't kill the mood. Sometimes doing that is really hot — you can tell her how you thought about her at work all day, or bring up a different time you guys fucked and tell her what you liked about it. If you're into rough sex, you can do things like tell her how stressed out you are and why and how fucking her is the only thing that helps you blow off steam. Don't like ... ask her how her grandma is doing while you're fingering her asshole or anything; I'm just saying that sometimes, you can eroticize the "How was your day?" conversation some people need to have in order to feel connected. You feel me?
And, since you seem to be feeling a little overwhelmed by her fuck-drive, I'd also recommend you have an open and honest conversation about the way each of you seeks intimacy and connection so that the other knows what they need to do to meet those needs. Very specifically lay out what makes you feel connected to the other person so they can be sensitive to how you communicate trust and love, then do your part to satisfy each other.
I recognize, though, that sex is different than talking in regards to how often you can do it. You can talk all day and not get tired, but you can only fuck once or four times before you fall asleep covered in each other's butt juice. Sometimes you can't fuck at all because one of you is too exhausted from commuting for two hours or has diptheria, and that really sucks, especially when fucking is how you express yourself.
So, for your sake and hers: are you aware that "sex" doesn't necessarily have to mean intercourse? It can be oral, finger-banging, toys, hot make out sessions, mutual masturbation, reading sexy stories to each other, rimming, erotic massage, sexting on the phone or computer, telling each other the dirty things you want to do to each other and, so on. The word "sex" is biologically defined as intercourse, but I'd really like to extend that definition to "anything arousing that builds intimacy."
As the person with the higher libido in my own relationship, and someone who, like your girlfriend, seeks connection and intimacy physically, I know your girlfriend probably doesn't need intercourse to feel satiated: sometimes, it's just physical energy or intimate attention that matters. You don't need to put your penis or strap-on in her pussy to make her feel desired; you can show her she's sexually valuable in a million other ways.
So, relieve yourself of the expectation and burden of constant literal fucking, communicate to her about how each of you seek connection, and find a way to compromise so that each of you feel you're getting the intimacy and attention you need in your own little special snowflake ways.