Your partner should not be closer to your friends than you are. If they are, you are not just sharing a social circle, you are diluting the foundation of your relationship. Connection thrives on exclusivity. When your partner blurs the lines between being your lover and being one of the group, you risk losing the dynamic that makes your bond unique.

How close your partner should be to your friends depends on what kind of relationship you want. If they are too distant, it creates division. If they are too close, it invites complications. Attraction needs space to breathe. The healthiest relationships have a balance where your partner gets along with your friends, but their connection never overshadows yours.
The real issue is power dynamics. If your partner is forming deeper bonds with your friends than they are with you, there is a shift in control. If you start feeling like an outsider in your own circle, that is a problem. When a partner integrates too much into your social world, breakups become more complicated, boundaries get blurred, and personal issues become public property.
If you find yourself questioning whether your partner is "too" close to your friends, you probably already feel the shift. That is your answer. Keep your friendships strong, keep your relationship strong, but do not merge them into one. Some lines should not be crossed.