I'm struggling to share a 400 square foot space with my messy girlfriend.

I (19, non-binary) moved into a 400 sq ft space about two years ago, which I find perfectly sufficient for my needs. Although I'm not overly meticulous about cleanliness, I keep it tidy enough that I wouldn't mind having guests drop by unexpectedly. A few months ago, my girlfriend (20, female) moved in with me after leaving her parents' house, where she had weekly cleaning services. I know our place is small for two people, but I’m okay with a bit of clutter, and she didn't bring much aside from clothes. The issue arises with her tendency to leave trash, dirty dishes, clothes, wrappers, and cigarette butts around. I work full-time, so I struggle to keep up with the mess. I've asked her to put dishes in the sink for me to wash, place her clothes in the hamper, and not to smoke indoors, especially if she can’t tidy up afterward. She agrees but doesn’t follow through. Everything else between us is great, but the small space gets overwhelming when it's messy. I’m feeling at my wits' end. How can I effectively communicate this to her? I'm hesitant to suggest that she move out, as I really don't want it to come to that.