Advice on how to tell your mom that you’re pansexual and genderfluid?

I feel that honestly you just need to come right out and say it. You are her child, she will learn to love and accept you for you are. Just find a comfortable time and place, and say it in the most sensitive way. If you keep the band-aide on too long, it will just keep getting harder to try to tell her, so rip it off, and just be honest with her. Best of luck to you! xx

In my opinion, I dont think that you should come out to her. Wait until you leave home or she changes her views. Everyone always says that coming out is the best thing you can do, but in your circumstance I dont think it would be. You should be safe. There are always other people that you can talk about it to, like your sister. You need lots of support and coming out to your mum wouldn't be good on your mental health. Parents can be cruel.

You don't have to come out to her if you don't feel ready. Personally, I would wait until you have accepted it, and are comfortable with yourself. Then, when you do come out, you will be able to say with full confidence, "This is who I am!"
Personally when I came out I wrote a letter, because it was easier for me than talking. My parents were (and are) a little homophobic, although not as bad as it sounds like your mom is. I wrote about a page explaining everything, and at the end I said that I wanted to talk with them to make sure any questions or concerns they might have were answered.
I also included a list of resource links. I felt this was important because they were probably going to google it anyway, and I wanted them to have a list of reputable sources. I don't know if they ended up looking at anything on the list, but I have a suspicion they did.
That's what worked best for me... but depending on your relationship with your mom, and especially if you are still underage or relying on your mom for finances, you will have to come up with an approach that works best for you. Again, I would also try to come to terms with it yourself first, because if she reacts in the same way as she did to your sister, it will likely be much easier for you to deal with than if you came out to her right now.
Good luck, and I hope everything turns out well for you!

I don't understand why anyone needs to come out. Be who you are. We all just need to learn to accept everyone. i didn't announce that I was heterosexual, why do you need to explain youre sexual orientation. Everyone just needs to accept there are many differences between us and we all just need to be tolerant. It shouldn't matter who or how you love. If you have a special someone to introduce to family you may need to have a conversation but until then you do whatever you need to. Love yourself, be you, don't allow others judgements to interfere with your happiness.