How would a character react if an old girlfriend shows up in a story?

Most likely, the character would be very confused. They would wonder what had happened and might immediately start trying to think of ways to reverse the situation. They could also be a bit scared, especially if they don't understand what's going on. For example, if they were used to having a male body and all of a sudden have a female body, they might be worried about how to act and how others will react to them.

Well, she might come back to seek closure. Maybe there were unresolved issues between her and the protagonist in the past, like an argument that ended their relationship abruptly. And now she wants to talk it out, to finally have a sense of peace about what happened.

She might be initially shocked and confused. She would probably look at her new body in disbelief, trying to figure out what had happened.

Clint Barton would first and foremost ensure her safety. He'd take her into the house and get his family to help if possible. He'd call in any favors or use his old SHIELD connections to get medical help if needed. He'd be on high alert, knowing that if someone was able to injure Black Widow, they might be able to track her to the farm. His reaction would be a mix of loyalty to his friend and the need to protect his home and loved ones.

Naruto would probably be initially shocked. He's a very loyal person, so he'd have a hard time believing it at first. Then he'd likely be very angry. He has a temper when it comes to things that are unjust, and this would be a huge betrayal. He might also feel really sad and disappointed in himself for not seeing the signs earlier.

Most people would be shocked and confused. It's not something that is expected in a normal relationship.

Some people might immediately side with the girl, especially if they find out the boy was in the wrong first. For example, if he was the one who started the trouble by being aggressive.

They might be cautious. After all, they don't know her and she's from Percy's world which could be full of unknowns for them.

Society would generally be appalled. Such behavior violates basic family ethics and social moral standards. People would likely condemn the mother involved as it goes against the expected norms of family relationships.

I would feel jealous and concerned. It's not just about the act of tickling itself, but what it represents. It could imply a certain level of familiarity that should be reserved for the relationship. I would start by having an open and honest conversation with my partner. I would explain that this makes me feel insecure and that I expect her to be more aware of such situations in the future. I might also set some clear boundaries with her about interactions with other men to avoid similar situations from happening again.