In future heterogeneous cellular networks (HCNs), the device-to-device (D2D) communication is considered as an efficient technique emerging mobile social network (MSN) services. Due to spectrum reuse among devices, the D2D however also brings in more interference, which will cause degradation in spectral efficiency (SE) when the density or centralization of devices is relatively high. With the help of control and data planes separation architecture (SARC) in the HCN, a smaller granularity of cooperation at device level is expected to be available for interference mitigation. Therefore, this letter introduces the coordinated multipoint transmission (CoMP) into D2D- enabled MSN to enhance SE performance. A CoMP scheme based on the average received signal power is designed for the D2D-enabled MSN (namely MSN-D2D- CoMP), on which basis the SE performance is analyzed using stochastic geometry for a hierarchical HCN with underlaying D2D devices. It is shown that MSN- D2D-CoMP effectively helps mitigating interference and outperforms the conventional paired D2D in SE (38.4% on average according to simulation results). And the gain of MSN-D2D-CoMP in SE increases with closer social relations for devices.