Sagittarius girls are passionate and unrestrained, like freedom, and have a naive and delicate personality. You should give them some thoughtful small gifts. Since you are good friends, you should know her very well. You can pay attention to observe what she needs in her daily life, preferably something practical.
Also think about what she wants to buy but can't afford to buy, and buy her a luxury gift on her birthday. She will be very touched.
Others can also consider buying some cute small gifts, small pendants, small toys, and now that it's cold, you can also buy a plush glove, which can be used when watching TV or surfing the Internet at home, which is very warm.
If you have enough money, you can give her some big things, such as a piece of clothing or a bag. You should know her taste very well, and things like clothes are worth the price. How much you spend can fully reflect it. It is much more affordable than cleaning up. Consider it.