How do I break up with my long distance girlfriend without breaking her heart because like she texts me a lot asking me to promise to never leave her which is hard to be like “well I don’t promise that because we’re seriously 15 years old”, and she says that she loves me too much and just all this stuff and I cANNOT DEAL ANYMORE AH—

Anyone got any advice for this (extremely childish, I know) problem? 😅 I don’t want to break her heart but at the same time I am just kinda uncomfortable with this stuff but am too scared to be honest about it.