Have you tried talking with your mom about any trans issues, to "test the waters" so to speak on her feeling about transgender people in general? And even if it isn't quite as warm as you would perhaps hope she's your mom, and it seems like you two have a good relationship. It tends to be a whole lot harder to have a guttural hatred from something when it's staring you in the face as close family not just "the other".

I haven't yet sadly she's very openly against lgbtq topics she can tolerate them as long as she doesn't have really anything to do with it I wish she was open about it

there is really only one way to come out. That is to simply be out with it. Beating around the bush will never cut it as it will leave to much to their interpretation and then you are stuck explaining anyway. What Penny said is a valid way to address the prepping for it. While she is avidly against those things, its really easy to destroy something that you don't have any connection to, its a whole other issue when you have a good connection to it. Something to think about. She may be against it just because of the general sheeple mentality that the USA has. Very few think for themselves on topics that they know nothing about. Rather than researching it and using critical thinking skills to come up with their own ideas they simply take whatever side is presented to them and that is how they will think. So educate her. Now I will say that you don't have to do anything at all right now. Transition is not a lightswitch. You are not going to start today and be done tomorrow. It takes at the barest minimum 1 year to complete. I recommend taking longer than that personally but each has their own path. So for the 1 year it would be starting tomorrow which means throwing away your entire wardrobe and getting new starting all the name chance stuff and so on. Assuming you are not going to do that, and going to gradually work into it, why say anything right now. Start with the therapist and go. it will take a while for you to get to hormones and even then it will take a couple years for it to completely effect you so it will give you a year and some to make the choice to come out. So if you want to come out great, just go out with it, that is your best option, and understand that their reactions will vary and you have just given them a MAJOR shock so the initial reaction may not be the official reaction. If not then you have time to figure it all out and move in slowly.

I have to agree personally with WyndWytch because personal experience with my father feeling the same as your mother does was a huge hurdle for me to jump over. ultimately though when I finally was able to be honest with myself and show myself my own truth, it got so much easier to show everyone else, my family included. I grew up in an uber-conservative catholic family and many of them took issue with me being trans. that being said, it isn't their life, it isn't their happiness at stake...

Make sure you are living independently and your family can't control you or force you in another direction. We implicitly trust our families but they often try to muscle us back into place when we step outside the box. If you are living with them, it can become unbearable. I encourage you to make whatever decision is best for yourself, but if you involve them too early, they'll think they can change your choices.