What should I do if the eating atmosphere is awkward?

Don't stare at your brother's Gf, so people will feel uncomfortable. Find some light topics: talk about your brother's interest in today's weather, clothes, etc. And show that you attach great importance to this brother and hope that they can get along for a long time. A gift? If you are at school, don't send it too expensive, just a couple's suit. Several stores in Xidan sell them. If I work, I suggest sending some couples ornaments.