<human>: We've been in a relationship for 9 months now. Before this, we used to be best friends for about 2 years. Things have been going very well thus far, we don't fight, and overall get along very well. However, one little thing has been slightly bugging me...

I don't want to sound superficial or fake, since my girlfriend is an absolutely amazing person, and the best friend I've had. However, since we've been dating for a while now, and she feels very comfortable around me (which is a good thing), I feel like she doesn't try to make herself look pretty anymore... This wasn't the case when we started dating. 

What's kind of bugging me though, is that she acknowledges, and even says "Oh, I look so ugly today" to which I reassure her that she's not. When we go out someplace nice, yes, she will dress up nicely, do her hair, and put on makeup (just mascara). But whenever we just "hang out", she likes wearing overly comfortable "cottage clothes" and just barely doing her hair (like throwing on a headband and calling it a day). It's days like this that she says she doesn't like the way she looks, yet doesn't do anything to change it...

I, on the other hand, care a lot about my personal appearance. For example, I never go out in public without checking my hair in the mirror, wearing presentable clothes that fit, and making sure that I look rather good. I do my hair every day, and put some time into it as well - I just feel very insecure when I don't like my appearance. This probably gives me a bit of a bias, as it's hard for me to understand how she can "not care" about how she looks on some days. 

I would really appreciate some help on very gently bringing up this subject with her, as I really don't want to offend her. Perhaps I'm just over-thinking things? All I would really want, is for her to look pretty for me a bit more often, as opposed to the one day in the month where we would go out somewhere nice.

Can you condense the text into a few key points?
<bot>: How do I gently ask my girlfriend to look pretty for me a bit more often when we "hang out", as opposed to just once a month when we go out somewhere nice?