LES question, what should I do about P's parental issues

I don't know what city you're in because LES, unless it's a particularly developed and developed area is understood.

I would suggest that you listen to your girlfriend and hide it from her mom for now.

Then, you can try to get her mom to reach out and learn something about LES through some behavior.

Many of your relatives around you have learned about your situation, maybe one day her mom will also know

But, compare to her mom who is also a parent, at first there will be resistance, but if time passes and she learns about her daughter's gender orientation and can't change it, she will also acquiesce.

Don't think too much about it now, it's the feelings of the two of you that are most important.