Hey Kayla❤
Reading your story made me realise how similar we are. I can also safely assume there are others like you who are reading them right now

It takes a lot of courage to come out to yourself, speak to people, let alone start on hormones. The fact that you are here, sharing, shows how important is it for you to make people know that you exist and you like most of us were unfortunate to be born in the wrong body.
We live in a very modern world, with medical science, anything is possible, you will have to stop worrying about other people, including your mum and do the right thing that is going to ultimately make you happy. Your mum or anyone for that matter is not going to be here when you're older regretting you didn't do this earlier. This decision must come from you. There's no one here that will be able to give you what you want until you decide this for yourself.
One other important factor that you need to remember is that no one here chooses to be TG, we have taken this step to medically alter what is given and live the way we want. If you believe that this is impossible then there wouldn't be any TGs, any of us let alone this forum.
Please also remember that you've already come past the first few steps, you cross-dressed, talked to your friend, even spoken to a therapist that confirmed that you're a transsexual. So why are you worried? It's a condition and there's help from everywhere.
I only wished that there was someone that I came out to, or even spoken to through this forum, and didn't go down the road of pretending to be gay only later to realise that I cannot hide the fact of who I truly am. So you know, I've only been on HRT for just over two years...
Yes, it is going to be a huge challenge, but the end result would be so pleasing you'll be the happiest girl in a very short period.
Also, As some of the others who've mentioned here, you can decide if you want to be non-op like myself. It is entirely up to you...

Take care,
G