Is it wrong to treat a selfless person selfishly?

I've been with my girlfriend for 10 years, and she has an issue with my personal space. I can be standing in a grocery store with 2-3 feet around me, and she'll stand against me, sometimes even near enough to touch. She'll sit so close we touch, sometimes even sit on my lap, and she'll also stand near me when I'm reading. Shes been doing this for years. I have tried mentioning my need for space, and she just says that she likes being "snug" with me. I want to start punishing her by treating her selfishly. I usually keep her happy, I clean the house, do her laundry, and cook all the food. I'm thinking of refusing to do all of these things for her because she won't respect my space. Is this a justified response to her selfishness?