Maybe you could acknowledge her fears and tell her what safety precautions you have.
Some things are hard to get your head around as a parent or guardian. For example I use Youtube for music and occasionally how to vids, whereas my cubs think of it the way I thought about TV at the same age. So I've had to change the way I think about what they are doing and compromise, but they have had to understand that regardless of what activity it is (chatting with friends, watching stuff, playing games etc) the total time on devices is also and issue.
But the main thing is I know it feels like your life would be over and I don't doubt it would totally suck, but I promise, looking back in a few years, it won't seem as significant. So hang in there
Do you mind if I ask how it is that your aunt is in charge? People taking on a parental role for another family member can often overcompensate in protectiveness.
