" There seems no reason to add "well". This has roughly the same kind of meaning as the original, but I'm not sure it exactly captures it. When you say "She is useful to all who know her", it sounds as if she is in an inferior position compared to those whom she is useful to.
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bepleasedMay I say so?"She is a useful person (so we get) to know (her).""She is a useful person so we get to know her" is grammatically possible but the present tense "get" is unusual there. It would be more usual to say "...so we got to know her" (past) or "...so we should / must / ought to get to know her" (suggesting what we should do in the future).