Any ideas on what the main conflict of my book should be?

im writing a book just for my enjoyment about the life of a teen named anna and hel best briend emily. i cant decide on what the big conflict of my book should be. i dont want something really tragic or depressing like one of them getting knocked up or diying, more of a heart touching kind of thing. something that will make the persone reading it cry from happy ness, or because it is so sweet. any ideas? im kinda stuck at 40 pages.... i was thinking maybe something that could happen that would bring my characters closer in friendship like on of their mothers dying, but thats so sad. :( any ideas are appreciated! thanks :) oh by the way im not publishing it or anything its just for fun!