I never became a Witness, but I did take the time to learn to read Greek. I also looked into Hebrew, but never got to the point of being able to read it. Along the way I decided that the Bible was mostly myth so it didn't seem quite as important to finish my study of Hebrew.
At the time it seemed that the subject of God and the Bible was important enough to justify the effort. Even though I am a not believer, I'm still very glad that I studied the Biblical languages.
To bad the lady didn't accept a study. She may have been able to teach the Witness a few things about the OT.