In 'Pride and Prejudice',why was Mary's performance bad compared to Elizabeth's?

Question

Mary, who having, in consequence of being the only plain one in the family, worked hard for knowledge and accomplishments, and was always impatient for display... had neither genius nor taste, and though vanity had given her application, it had given her likewise a pedantic air and conceited manner, which would have injured a higher degree of excellence than she had reached. Elizabeth, easy and unaffected, had been listened to with much more pleasure, though not playing half so well; and Mary,at the end of a long concerto, was glad to purchase praise and gratitude by Scotch and Irish airs, at the resquest of her younger sisters, who with some of the Lucases and two or three officers joined eagerly in dancing at one end of the room.

What do the lines in bold mean?

Answer 1

a pedantic air and conceited manner, which would have injured a higher degree of excellence than she had reached.

Mary's "pedantic air and conceited manner" made her playing less appreciated, and it would have done so even if she had played better than she actually did. (It's unclear to me whether the "pedantic air and conceited manner" was in her playing or her general attitude, or both.)

Elizabeth, easy and unaffected, had been listened to with much more pleasure, though not playing half so well

Elizabeth was not technically as good a player as Mary, but she was "easy and unaffected" (not at all serious or pretentious), and people enjoyed listening to her more.

Mary,at the end of a long concerto, was glad to purchase praise and gratitude by Scotch and Irish airs, at the request of her younger sisters.

After Mary had played her concertos (complicated and difficult pieces), her younger sisters would ask her to play airs (simple dance tunes). People praised Mary for those tunes, and Mary was glad to have the praise.