First, prove intimacy.
To know that the bitten person is in such pain, girls understand that they can't just walk over and bite a friend or colleague. If she is willing to bite you, it means that she trusts you very much, or that your relationship is very close. She knows how to hurt you, and you won't be angry or blame her.
Second, coquetry
Biting you is also a coquetry. Have you noticed that she doesn't bite hard every time? If she will bite you gently, she must be coquetry, just like meow and dogs like to bite gently when playing with their owners.
Third, declare sovereignty.
That is, the concept of "occupying territory" leaves a mark on a boy. When other girls see it, they will be well-advised to leave. Don't hit on my boyfriend because he is mine!
Fourth, lack of security.
Your girlfriend may bite you because she is insecure. She can't find a sense of security at the spiritual level, so she will use this method to build a sense of security at the external level, that is, bite you hard. Because biting is actually a sign of dependence and trust, in fact, she wants you to know that you are very important to her, so she wants to leave a mark.
Fifth, increase interest.
Biting you gently is actually a pleasure. In addition to cuddling, many girls also like to suddenly bite boys when making out.