It seems like you have both chosen this as your hill to die on.
You can decide you don’t want a social media account and deactivate, you know, for privacy! Or block her, knowing she can still post non-tagged photos of you, on her page, or you can wage war against your 50s ish aunt who likes sharing her happy memories with strangers on Facebook.
How are you going to change her mindset and make her care about your personal feelings? Why not sit down and talk to her, face to face, like an adult? Write down what you want to communicate, behave calmly and with respect. Meet her halfway.