Sadly, they might be separated by external factors like their families moving to different places. They try to keep in touch at first but gradually lose contact over the years. However, they always remember that special time in their childhood when they had those innocent feelings for each other.
One possible ending is that they remain friends. As they grow up, they realize their feelings were more of a childish infatuation. So they stay good friends throughout their school years and beyond, sharing memories and still caring for each other in a platonic way.
One possible ending is that they find a way to turn the zombie boy back to normal and live happily ever after.
One possible ending could be that the little girl manages to escape. She finds a way to outwit the Slender Man, perhaps by using some kind of magic or a powerful object she discovers. Another ending could be that the Slender Man catches the girl. But instead of harming her immediately, he takes her to his lair and she has to find a way to free herself from there. Or maybe the girl's family or friends come to her rescue just in time, scaring the Slender Man away.
Another ending could be that she is found after a long and difficult search. Authorities like the police and search and rescue teams might be involved. They could use things like dogs to track her scent. After hours or even days of searching, she is finally reunited with her loved ones, often with a great deal of media attention and public relief.
One possible ending is that she is quickly found by her family or the authorities. For example, if she stays in one place and her parents retrace their steps, they will find her safe and sound.
One possible ending is that they graduate and get married, starting a new life together. For example, like many campus couples, they overcome all the difficulties during study and finally build a family.
One possible ending is that the love between the homeless girl and her partner helps her get out of homelessness. They build a life together, find a stable place to live, and the girl gets the support she needs to pursue her dreams, like getting an education or a job.
The ending could be that they stay together forever. The girl might find a way to live in harmony with the wolf in the forest, building a little home where they can be together. They continue to love and protect each other from all the threats around them.
One possible ending is that the rich girl's family opposes the relationship, and the two are forced apart. Another could be that the poor boy, through his hard work and determination, manages to improve his situation and win the acceptance of the girl's family. Or perhaps they run away together to start a new life away from the constraints of their different social classes.
One possible ending could be that the girl and the boy's act of cutting (maybe hair or something symbolic) brings their families closer. Their families, who were initially against their relationship or friendship, see their courage and determination and accept them as they are.