This... this is not how you end a story of a kid being abandoned by a parent... resentment? hatred? indifference?
After all the things that she had been through, all of the things that she felt, in the end she is still playing not be cause of her own volition or because she truly love the sport, but still because of her mom. She did not grow at all, not one bit. I mean why? Why didn't she understand that her mom does not harbor any feeling towards her? Why make this kind of ending?
ARRRGHHHH!!! fuk it, I'll just trust my head cannon.
1st timeline
She broke down down the line but got back up, then played badminton again, this time not because she wants to impress, but just get better at the game that she loves.
2nd timeline
didn't go back to badminton and played tennis instead.
Edit:
I stand corrected,
"Why didn't she understand that her mom does not harbor any feeling towards her?"
The mom did felt something... It was sadism, a perversion of the innocence of not only Hanesaki but also to Connie
and to add, Assassination Classroom handled this kind of situation better.