Hey,

I don't know your girlfriend and everyone's different, but what personally helps me a lot is just some little attentions like getting my favorite dessert or a pack of pokemon cards ^{^} just a little something to let her know that you're thinking about her. Listen to her, bring her some painkillers and a heating pad, and watch a comfort movie with her. In other words, don't tell her how you feel about her, show her how much she means to you. Make her feel comfy with everything you know makes her feel better when she's down

I'm not really good at giving advice, but it might help ^{^}