There really isn't a way to help...? Tell her.
You know what's going on with your body better than she does.
I just got discharge this morning and i don't know how to tell my mom , and if I do I'm afraid she will say it wasn't discharge or say I don't need pantiliners , HELP?
Tell her what you just told us.
If your mother hasn't already talked to you about the changes in your body as you grow older then now is the time. Tell her what's happened, it's perfectly normal, but you need to be able to talk to her about this even though you might both be uncomfortable. If you think this might be something abnormal then ask your mother to take you to the doctor.
As a last resort you could talk to the school nurse.