'They lived beyond their income, but still it was nothing in comparison of Enscombe: she did not cease to love her husband; but she wanted at once to be the wife of Captain Weston and Miss Churchill of Enscombe'. Ch.2
Captain and Mrs Weston married for love and both appear as sociable people. I find an 'unsuitable connection' more complex than their personalities.
My impression is JA's comment on the 'unsuitableness' of the match refers to the first Mrs Weston's lack of resolution to fully commit to the match- She didn't find much happiness due to regrets over the family quarrel and missing her position at Enscombe.