It's very creepy the way she's acting. It's basically an adult lusting after a 13 year old boy.
Kinda? I mean... Yeah her mind is notably older, but this is someone she spent so many years getting to know and falling in love with. If you were in love with someone for years and went back in time could you honestly say you wouldn't still love them and want to be with them?
There's definitely a major mental age gap which is bad, but this is someone she loves because she spent a long time with when they were the same age, and would want to continue to be close to as they grow older. You can't really go "yeah I'm gonna wait 5 years to form a bond with you in this life" with the person you love, he'd form different bonds instead.
She loves him because of who he was as the same age, someone he'll be again in time. There's also the matter of how her brain is physically as young now, yes she has a lot more knowledge which is half of adulthood, but half of what makes a kid a kid is brain development she's lost too.
All in all, it's a prickly subject, and I agree there's issues, but ultimately the only solution she'd have left is "go off to a monastery".