You’ve likely teased her 50 times when she didn’t like it. You keep saying you teased her and she didn’t seem to mind, but before this part of the story she essentially almost always minds. It’s just that she doesn’t mind that much. The lines you’re describing getting; that you seem to think means she doesn’t mind; are not the lines you’ll see later in the game when she truly doesn’t mind. (Later in the game she starts to enjoy the teasing fully.)
The number required to pass this check is very easy to hit. I’d try loading a save that’s 5-15 days in the past, if you have one. Then just doing a bunch of stuff like letting her pick the movie, and the other ones players have mentioned, not doing anything to raise her weight for a couple weeks and then trying the check again.
In the test run through I did when I made sure alice was constantly mad at me for lack of romance score, I got the gameover, then essentially replayed one/two weeks leading up to it, and managed to get the non-gameover result.
IMO this check is totally fair, you’ve essentially been a jerk dozens and dozens of times.
Also, there aren’t limited save slots. In my folder where I was testing for bugs I had like 500 save files. You can just infinitely hit right to get more pages for saves.
In testing when I WANTED to get the game over, the best way to get the game over was just to spend the first week or so calling her and teasing her like 50 times, then you’d be nearly doomed to get the game over (although if you were nice to her the rest of the time you could still pass it.)
Checking the code you need a minimum of 20 aliceromance to get past this variable check. Of course it’s hard to know what 20 means without any reference points. (And more like 65 or so to avoid the breakup entirely.)
Some examples though, going to the fancy restaurant? +3 romance score.
Letting her pick the movie at the movie cinema? +1 romance score.
At your house watching the romantic movie, choosing the wrong option -1 romance and choosing the right option +1 romance.
Calling alice on the phone and choosing the tease option? -2 romance or -1.5 romance or -1 romance depending on how much she dislikes being teased. (You might have been getting some of these partial teasing penalties rather than the fully teasing penalty? If you noticed that the message changed a bit, you might have assumed she was fully into liking it, but she was actually just moving towards cutting down the romance penalty, not removing it entirely (like happens later in the game.)