@Krrypton,
Get over it and move on. You'd be surprised how many more people you'll meet that has the potential to become someone special. I wouldn't worry about anything permanrnt until you're in the late twenties.
When young, it's natural to keep looking. If you're not engaged, they're free to roam unless you had promised each other about not dating others.
Love is based on mutual respect - over a long period of time.
You didn't say how old you were or which grade you were in.