She might be initially shocked. After all, Draco is usually seen as this tough Slytherin. But then she could feel sympathy. For instance, she might offer him a handkerchief without saying much at first.
Hermione could start asking him what's wrong in a gentle way. She's a very empathetic person, despite their differences. She might sit down beside him and listen attentively as he pours out his problems.
It's also possible that she's a bit hesitant at first. She's not used to seeing Draco in such a vulnerable state. But then her natural kindness takes over, and she tries to comfort him, maybe by sharing some of her own experiences of feeling alone or under pressure.
Often, Harry will offer her a handkerchief or a tissue if there is one available. He might also put his arm around her in a comforting gesture. In 'The Common Room Crisis' fanfic, he does just that and then stays with her, listening intently as she pours out her feelings. He is patient and understanding, which is in line with his character in the original books. He tries to make her laugh or at least smile by sharing a joke or a funny memory. This shows his deep friendship and care for Hermione.
He might be initially startled. Snape is used to seeing Hermione as a strong - willed and confident student. So seeing her crying could catch him off - guard. But then he might quickly put on his usual cold facade and ask her curtly what's wrong.
She probably comforts him right away. Hermione is a very empathetic person. She might give him a big hug and let him cry on her shoulder.
Sirius would probably be very concerned. He might immediately ask her what's wrong and offer her a handkerchief to dry her tears. He has a bit of a wild side, but he also has a big heart, especially when it comes to those he cares about or sees as in need of help.
Perhaps he's had a falling - out with his friends. In the Slytherin house, there could be a lot of power dynamics and rivalries. If he's been betrayed by someone he thought was a friend, it would be very upsetting.
Hermione could become withdrawn. She might isolate herself from her friends for a while, spending her time in the library trying to make sense of it all. She might also feel a sense of betrayal, especially if they had some sort of understanding or relationship developing.
He might be shocked at first. Draco, despite his past rivalries, could feel a sense of protectiveness. He might initially struggle with his own beliefs and prejudices but then decides to help Hermione in secret. He could use his family's resources to make sure she is safe from further harm.
In many fanfictions, it can be a turning point. For example, it can make Draco realize that Hermione is more than just the 'know - it - all Gryffindor' he thought she was. It softens his view of her and can lead to the start of a friendship or even a romantic relationship.
She might be heartbroken at first. Hermione is someone who invests deeply in her relationships. She would likely retreat into her studies as a way to cope, burying herself in books to try and forget the pain.
One great fanfiction with this scenario is 'A Chance Encounter' where Draco stumbles upon Hermione crying in the library. The story beautifully shows how his initial shock turns into concern and how they start to see each other in a new light. It's a really heart - warming read.