A tight first round ended with Spencer 3-2 in front, having forced a standing count on Li with a furious attack, although not much was landed by the Canadian.
Li came back strongly in the second and managed to overturn the deficit to lead 7-5 at the halfway mark.
The Chinese fighter had settled into the contest by the third round and was exhibiting some smooth skills.
Spencer still found herself trailing by two as they entered the decider. The referee issued Li with a warning early on to level the scores.
Despite that boost, the Canadian was unable to get over the line and Li took a 17-14 decision.