I know it seems as though everything your gf talks about is boring or irrelevant, and while that might be true to an extent, keep in mind that you probably talk about ish she doesn't care about/can't relate to but she still listens bc she cares about you and pays attention anyways...it's a pain in the ass at times; and I definitely can feel you bc my bf is a real chatty patty while I'm not,(I'm a writer so Im more apt to writting things not to mention it's easier for me to put my thoughts on paper rather than verbalize them)I suck it up and listen to him prattle on (and on

) bc it makes him happy, and I don't want him to feel like he can't be himself with me...it's a part of his personality so I just listen...do I tune some of it out? Hell yea lol especially when I'm fresh off work and aint in the mood but it's what you do when your in a relationship...you compromise.
When I find myself getting irritated with him because of all the talking, I
listen anyway and imo you should too, and if you actually listen to what she's saying it might not be so bad, but the more you try and tune her out the more annoying it will be to you
Just let her talk and really make an effort to pay attention so you can give her good feedback, trust me on this, actively participating in even what you might think is a pointless conversation with her can spark a really good dialogue, and if it doesn't at the very least she'll be able to get it all out at once rather than her repeating the samethings in different ways over and over all night lol
So to answer your question NO. Don't tell her she's annoying bc it'll most definitely hurt her feelings, and make her feel self conscious about talking to you bc in the back of her mind she'll be worrying about weather or not you're really listening and if you're making the

face in your mind...it's just one of those things you do to make her happy just like the things she does for you