i don't know enough about ancient languages to comment on what exactly is meant by the word translated "congregation" or "temple" but that may be one way you could go (i.e. you could show her that the original thought behind the word 'congregation' or 'do not forsake the gathering...' does not necessarily demand the definition that JW's give these phrases. i know others on this board have posted this kind of material relating to the scripture in Hebrews).
if your ma is anything like mine, it won't matter, but just the same.
i like to point out that the early christians usually met together in small groups of 3 or 4 in their own houses. no where in the bible does it define a congregation as "at least X number of individuals meeting at a place specifically designated as place of worship". it just says continue to hang out with each other. that's just good advice.