While it is a zechut to do many mitzvot, we don’t know what makes one mitzva more difficult for another individual. Maybe she was tired from whatever she was doing, or could not really afford to make her mishloach manot the way she wanted to…Or maybe she had other things going on in her life that would make this mitzva a burdensome one for whatever reason.
Bottom line–the way a person does a mitzva is between him/her and God.