Hormonal factors can play a role as well. Certain hormones like oxytocin are released during sexual activity. This hormone is associated with feelings of bonding and pleasure. So, her body's natural chemical reactions could be contributing to her not being able to get enough of their sexual relationship. Also, if her partner is very attentive and caring during sex, it can make the experience extremely fulfilling for her, leading to her desiring more.
One possible reason could be the strong emotional bond. When a woman is deeply in love with her boyfriend, the physical aspect of the relationship can be enhanced. The intimacy might make her feel closer to him on an emotional level, and that in turn intensifies her enjoyment of their sexual relationship.
It might also be due to the novelty and exploration in the relationship. If they are still in the early stages or constantly trying new things together, it can create a sense of excitement. For example, exploring different locations or trying new techniques can keep the spark alive and make her crave more of those experiences.