This idea may be caused by emotional dependence and the sense of security brought by intimate relationship. When you hold your girlfriend, physical contact and intimate atmosphere will make you feel safer and more supportive, so you will feel like you want to integrate the other person into your body.

In addition, sexual attraction may also lead to this idea. Everyone's body and body odor are unique. There is a strong attraction and mutual attraction between you and your girlfriend. In some cases, this attraction may make you feel like you want to integrate the other person into your body.

However, it should be noted that this idea does not necessarily mean real integration or spiritual unity. You are still yourself, your girlfriend is still herself. This feeling may be just an emotional experience, not a real reality.

If you are confused or uneasy about this relationship, you can talk frankly with your girlfriend and ask her about her views and feelings. At the same time, you can also seek the help of a psychological counselor to understand how to better handle this emotional need.