Single-photon emitters (SPEs) are crucial in quantum communication and information processing. In 2D transition metal dichalcogenides (TMDs), SPEs are realized through inhomogeneous strain, while in combination with 2D magnets, a high spontaneous out-of-plane magnetization can be induced due to proximity effects. Here, an alternative is proposed that consists of suspending a TMD monolayer (WSe) on a few-layer antiferromagnet (CrSBr) with in-plane magnetic ordering. The resulting heterostructure exhibits localization centers at lower energies than expected. Among them, a bright SPE with a high degree of polarization selection is identified. This suffers a clear energy shift driven by an in-plane magnetic field, and interestingly, this shift is correlated with the metamagnetic transition of CrSBr, suggesting a new kind of proximity-type effect. Unlike regular SPEs in WSe (sensitive to out-of-plane magnetic fields), our SPE demonstrates sensitivity to both in-plane and out-of-plane magnetic fields. The added tunability at significantly lower fields offers a promising direction for developing magnetically responsive quantum emitters, paving the way for more practical applications in quantum technologies.