What is the level cap when power leveling a lower level character POE 2?

I have a friend who is playing a level 31 Witch. I am level 83. I powered her through all the story, but she cannot do endgame until 50.

We went to a level 60+ area, and after playing for an hour she got 1% ex.

We went to a level 36 area, and she was getting massive exp. Once she got to level 37, we went to a level 50 area, and she was getting exp very quickly.

My question, is what is the maximum area level a person can be in at level 31? I know some games have a 10 level gap, and others have no restrictions.

A 5 level difference has been a consistent sweet spot when I tested XP.

I know it is greater than 5 levels. I just want to know what it is, if anyone knows.

7-8 if im not wrong

She was level 38 in a level 51 area. So it is more than 7-8 from what I have seen.

I have not seen any published data for POE2, but it is assumed to be similar to POE1. Have a look at poedb.

In 1 you get 100% up for +/- 3 levels, then there is a drop off per level. By +/- 10 levels it's down to about 5% of possible xp for the level of mobs.

Look here for a exp table:
https://pathofexile.fandom.com/wiki/Experience#Experience_penalties