Okay, on closer inspection, I think someone forgot to negate the call in the event condition. I didn't notice it at first, but the function actually checks if her experience is less than the provided value. I read some context for its use just to make sure I wasn't missing anything, and yeah, that seems to be the case and intentional as well.
The problem is that this particular event uses it as a condition, and doesn't negate the result of it like it does in some other places, so basically it calls the function with the parameter set to 10, which returns false because her experience is greater than that.
What the dev can do:
Add a "not" to the condition in the event definition.
What you can do:
Use console, Universal Ren'Py Mod, or method of choice to set her sexperience lower. You'll also need to alter a second flag which can otherwise mess things up for you as well: emma.flags.sexperience = 0emma.flags.loose = 0.
Alternatively, you can test the quick and dirty fix I made and attached. Just take the file and put it in the "game" folder inside (where a bunch of .rpa files are). I haven't tested it more than seeing that it seems to do what I want it to do, but just deleting it (and the compiled .rpyc file with the same name that will be created) is enough to get rid of it.