Hi Sunny123,
I have experienced having to distance myself from certain people during specific times in my life. My advice is to tell yourself you are simply taking a time out from this person. Because when you say (even just to yourself) "its over forever" or "i never want to see her again" you can end up beating yourself up over whether this is a "good" decision or not. Because it can cause anxiety to think about never seeing the person again. The reality is you have no idea if this will be a good friendship a year from now or not. So making really absolute type statements leads to wondering if you are making the best decision. It would be odd if it didn't since a friendship is a valuable thing and its hard to make an absolute decision about a valuable thing.
It is much easier psychologically speaking, to say "I need a break right now" instead of "we're done forever".I don't mean in terms of making her feel better, I mean in terms of you feeling good about needing distance.
Now there are people who can hear "i need a break from you" and they say "i understand" and wait for you to feel better and call them up and there are other people who freak out when you say "I need a break from you". In my experience, if the person is the latter type, I take the break without making a big proclamation about it to them. The reality is you need a break for a bit (at least) to sort out what this friendship is for you, and this person may or may not accept that. That doesn't change the fact that you need the break, it just means they are struggling to accept it. Being on the receiving end of such information myself, I can admit humbly that even when I wish I was mature enough to hear it, sometimes if I am down, and my friend says "hey by the way i need a break from you" I get sad even if I wish I were a bigger person than that. What I mean is, she may take it badly and it doesn't mean she doesn't care it may mean her feelings are hurt by hearing it.
Anyways, you should take the break you need and consider whether you can do that quietly if she will take it badly, i.e. just tell them you are busy the next time they ask to do something and then go from there. Breaks from people are not bad. Even people who love each other need breaks. There is nothing wrong with you needing a break and in the ideal world your friend would respond with "Wow. I'm glad you value our friendship so much that you are able to be honest with me about having energy for us right now or not and I am so glad you know how to take such good care of yourself by asserting your needs." These are the sorts of things really wise people might be able to say but it can take a long time for us to get there. I count myself in there. I have a friend right now who doesn't want as much contact with me as I want with her. She has been open about this. on good days I am glad that she knows how to assert boundaries because she has worked hard to become this strong person who can say what she needs. But on bad days of course I am upset she is not wanting to be my best pal right now.
My point is that your friend may feel she really wants you around and thus may react poorly if you tell her you need a break, but it is important for you to (like my friend is doing with me) stick to what you need. And friendships change over time, they are not static things. This person may be a better friend to you in the future, and making smaller , shorter time frame statements like "I just need a break from her right now" is more open ended than "we are done"
Although sometimes you get to that point but then when you get there with someone , you feel quite certain and the certainty feels good and the way you phrased your email it doesn't sound like you necessarilly want this person out of your life forever , just some distance.
If your friend responds well and says "when you feel it is the right time, we should talk about this" or something acknowledging your needs this will be a good sign you can use the conflict management skills in the toolbox with her. Its either in the toolbox here or some other site about relationshisp that i read that if one person doesn't want to resolve the situation then it can't get resolved because that person is basically not going to participate in making any changes or do any problem solving. Sometimes that happens. I hate to be pessimistic about people but some people don't want to improve their relationships with others because it makes them admit they need to change. But some people value their friendships and want to know if their friend is feeling suffocated by them.