@@bakabakabeyond YANBU at ALL!
This woman is nothing to you OR your son. It clearly doesn't feel right for you to continue you this friendship, and it doesn't bring anything to you, and you live 200 miles apart. She sounds very needy and possessive to me, and it won't be long before it turns toxic.
How the eff can she love your baby 'to the moon and back?'
She only knew him up to a few months old, and he is not even a real person yet! (No offence!)
She sounds a bit unhinged IMO. And no, she is NOT your son's 'auntie.' (Although it doesn't help, as a previous poster said, that you started referring to her as Auntie.)
And, if she is 10 years younger than you, and you are 'only in your 20s,' how old is she? Obviously teens I am guessing, so you may need to perhaps shake her off gently. Just let the contact get less and less, take 1 to 2 days to respond to texts and messages, and don't invite her to your place. If she tries to invite herself, put her off.