<human>: My girlfriend and I have been going out for 4 years (we've known each other for 9) and I noticed that she hasn't been making any effort to dress nicely, put on makeup and whatnot anymore. She used to do those things when we started going out but seems to have stopped caring the last year or so. For example, we recently went to a dinner party where she wore shorts and a t-shirt while everyone else (myself included) wore suits or dresses.

Don't get me wrong, I love her regardless and still find her very beautiful but I'm afraid there might be some underlying issue that I'm not noticing. 

I'm also not sure how to talk to her tactfully (i.e., without it coming across as "I don't think you're pretty") about it too.

Can you provide a brief rundown of the text in within 3 sentences?
<bot>: GF doesn't care about her appearance to the point of dressing inappropriately. Am I being shallow or is it possible that there's a problem that I'm not aware of?