I sent a congratulatory message to my girlfriend, and she said, thank you. How should I reply?

In fact, I don't like to accept greetings because I think it's unrealistic. It's just words, not something that can be touched. I can understand your girlfriend saying thank you. If I were you, I would reply directly, because I really don't know how to reply to you again. Do you want me to send you a congratulatory message? I feel embarrassed to reply too much.