A.T. Robertson Commentary Luke 10:42

"but one thing is needful: for Mary hath chosen the good part, which shall not be taken away from her." — Luke 10:42 (ASV)

The good portion (την αγαθην μεριδα). The best dish on the table, fellowship with Jesus. This is the spiritual application of the metaphor of the dishes on the table. Salvation is not "the good portion" for Martha had that also.

From her (αυτης). Ablative case after αφαιρηθησετα (future passive indicative). Jesus pointedly takes Mary's side against Martha's fussiness.