The claim advanced by your business associate is one of the more well-known arguments used by missionaries to defend the doctrine of the Trinity, the most guarded and untenable creed of the Church. It would be difficult to imagine a doctrine more hostile to the uncompromising monotheism preached in the Jewish Scriptures than the Christian claim that there is a plurality within the divine nature of God. Yet, armed with little knowledge of the Hebrew language, many Trinitarians brazenly argue that the name of God, as it appears in the first verse in the Bible, “proves” there are three distinct Persons in the godhead.
More specifically, missionaries point to the plural form of the Hebrew name of God אֶלהִים, (Elohim), which appears frequently in the Torah, to bolster their claim that there is a complex unity in the godhead. They argue that the use of the Hebrew letters “ ים” (yud and mem, pronounced “im”), which is a plural suffix at the end of the word Elohim, provides ample evidence from Tanach that there is a plurality within the nature of God. Your business associate went out on an even more bizarre limb when she declared that this Hebrew syntax is somehow indicative of the “plural form of three.”
https://outreachjudaism.org/elohim-plural/