I don't really know your mom, but mabye it wouldn't be so bad if you just told you that you tried experimenting. If I were a parent I'd probably be more heartbroken from my kid doing drugs behind my back and then lying to me than my kid that made a mistake, but atleast told the truth. I would go to your mom and just tell her everything and mabye try to disprove the flaws in marijuana that she probably sees. If you can't convince her that it's not as bad as she makes it out to be then mabye just try to compromise with her. If you're quitting then you might aswell just come clean and tell her you just wanted to experiment and now you're done with it.