I would not recommend doing that. Apart from possible breaking the game, your relationship stat is only a small part in your relationship with each girl. The game basically keeps track of all your interactions with all the girls and based on that more then your relationship stat it will allow you to do certain things.
For instance: If you break of your relationship with say Yvette, you can rebuild your relationship stat to 100 but you can never be in a relationship with her again. She will know you broke of the relationship.
or
If you lied to Michelle, she will be pissed of with you when she finds out etc. etc.
So you actually gain relationship stats relatively easy, but you can lose them just as fast. The game relies more on flags in the game to know what you have done in the past then just the stats. obviously if your stats are low you would fail as well, but normally your stats would be low for a reason and the correct flags for the event would not have been set in any case, making adjusting the stats futile.
If you actually look at all the variables the game use, you would see that trying to manipulate them is almost impossible. I'm helping Honeygames with the stats screen and I don't know the meaning of half the variables in the game. You would need to do a deep dive like
Erock to manipulate the game.