This work studies a simultaneous wireless information and power transfer (SWIPT)-enabled relaying network, where a power splitting protocol is applied at the relay before energy harvesting (EH). Due to low-latency requirements, the transmissions are operated with short blocklength codes. We aim at providing a reliability-oriented network design, while for the first time, the finite blocklength (FBL) impact and a realistic nonlinear EH process are jointly considered. In particular, we characterize the overall error probability of the considered network, and formulate the problem minimizing the overall error probability by optimally choosing the power splitting ratio. However, the formulated problem is non-convex due to the nonlinear EH process (which is also non-convex), thus making it challenging to be solved optimally. To tackle this difficulty, we propose a three-step approach to obtain an efficient solution. We first introduce two auxiliary variables, with the assistance of which we reformulate the problem. Then, we apply a convex approximation technique to tightly approximate the problem (at each local point/solution), based on which an efficient iterative algorithm (updating the local point) is finally proposed approaching a high-quality sub-optimal solution. Simulation results are provided to validate the convergence of the proposed algorithm and evaluate the performance in comparison to benchmarks with linear EH.