At the end, I got this feeling, that the one she called wasn't her ex boyfriend but a girl (like her friend) who confessed to her earlier before she got to live with her sister and her lover. After experiencing her sister's relationship with Ena, I felt like (just a feeling I'm having), she decided to give that person on the call a chance. I have this feeling that she realizes that dating another girl wouldn't be so bad, so she called the girl who gave her the cellphone strap (it looks more like a gift from another girl because of its cuteness lol). If the person she called at the end was the ex-boyfriend, she could have called earlier to resolve whatever issues they had.