It could be that she had an argument with someone over the phone and that made her cry. Or perhaps she lost something important related to the phone.
Maybe she got some bad news on the phone that really upset her.
The girl might be crying with the phone because someone she cared about broke up with her through a call. Or maybe she found out she failed an important exam or job interview via a message on the phone.
Maybe she received some bad news through a message or call.
Maybe she received bad news or had an argument with someone on the call.
Maybe she's sad because she lost something important to her.
Maybe she's sad because of a heartbreak or a loss.
Maybe she's sad because of a lost friendship or a heartbreak.
It could be that she's facing some emotional turmoil, like heartbreak or disappointment. Or perhaps she's feeling lonely and misunderstood.
It could be because of the way her expression and the surrounding context are depicted, creating an eerie atmosphere.
Maybe she's sad because she lost something important or had a fight with a friend.
It could be that she's scared of something or didn't get what she wanted. There are many possible reasons for her to cry in the manga.
Maybe she lost someone dear or faced a big disappointment.