Hi, Jai. I'm Kai. Welcome to MIB headquarters.

(Sorry, I couldn't help myself XD hahahaha) *rolls around on floor in amusement*
*Ahem* Ah, yes, anyways. I'm 27, also female, but never been too happy about it. I've only recently started thinking about transitioning. Although like you I donno how I feel about having to shave my face for the rest of my life, lol.
That must be rough having to deal with your grandma.

I can imagine how it must be. I haven't actually come out to anyone in my family yet. I am scared to.

Most of my family is pretty open minded and I think would understand, but my dad and grandparents are very religious and VERY homophobic and if I were to come out and tell them that their "normal" straight daughter/granddaughter has decided to live the rest of her life as a gay man, well, that wouldn't go over well at all. *cringe* And honestly it's not something I really wanna deal with. But it sucks, because if I do decide I want to transition, I will have a really hard choice to make. Whether to bite the bullet and tell them and risk being scorned and disowned by them or try to just live as both until they kick the bucket (which is sad to think about, but that's life I guess).
But I would say, since she already knows, and since you sound like you have very strong feelings about it, just do what you wanna do. You're an adult and I know it can be hard to pull away from the influence family can have on you, but trust me, you don't want to waste time trying to make everyone else happy. That's impossible. In the end, being happy with who you are is a lot more important than not making someone uncomfortable. Hopefully she will come to accept it more as time goes by. In the meantime, just give yourself some space to figure things out and try not to stress, and know there are kindred spirits here who are ready to offer you their support.

Also, (TMI WARNING!) I started growing weird random hairs around my nipples when I was around your age. It's actually not that uncommon, I hear. lol.