It is not necessary to wear some symbolism to defend your position. But if it's essential for your girlfriend, I recommend badges on a backpack or bracelets. These small accessories do not attract attention, but people who understand the topic will immediately notice them. By the way, you can give her along with a small gift basket icon. I always give a set of sweets to my friends when I want to please or support them. Sweet produces the hormone of happiness and improves mood. She can also order a hoodie with a pride flag.