I think Marinette's behavior is quite relatable from her standpoint (Illustrhater spoilers)

As someone who was a teenager, I fully get her backsliding into awkwardness with Adrien. I started dating my first significant other during a homecoming dance, and it was a magical experience and we really connected. But afterwards, there was a lot of second guessing and shock. How do you behave with someone you're dating when you're a shy and awkward person who has never dated before. There's a lot of insecurity and overthinking.

Couple that with the fact that she's dating a super model and she just fought and was partially responsible for his supervillain dad wishing himself out of existence (or at least, I think so, unless his spirit is helping Lila). AND she's responsible for like 15 superheroes, kwamis and the safety of Paris. And now there's somebody who is supposedly not a fumbling ham like Gabriel was half the time.

I am a Marinette fan but I do think I get where they're going with this and it's not instantly an Ash Ketchum scenario where they de- age him for future generations. I'll have to see more, but honestly, being a teenager alone is incredibly anxious experience and well, she must balance that with being Ladybug.