My girlfriend Alice and I have been together for the past 4 years, we're both 20 years old. I've recently decided to end our relationship for reasons related to some traits of her personality (e.g. anxious, lacking self-confidence, not quite lighthearted) and decreased physical attraction. But I can't do it right away because if I did, she would not be able to take her exams. Therefore I plan to tell her just a few days after them.
The thing is Alice suspects nothing at all. We have had contrasts but they've always been superficially temporary, as I try to be kind to her, even because she suffers from lack of self-esteem. In other words, she doesn't expect these problems are going to lead to a break-up. However, she irrationally fears it: despite me trying to push her to be more self-confident, she's always told me about being not enough for me, and that I shall leave her - even when I didn't want to. Relatedly, Alice has also often said that if I were to leave her, she wouldn't know how to live anymore, and even talked about suicide. I am pretty sure she won't do anything dangerous, but this is obviously not a healthy attitude from her - I've always tried to correct this, and even suggested to go to a doctor, but she always minimized, and after all she has me. I hope she'll have the courage to go after the break-up.
Also, Alice has an apartment way larger than mine, and we almost live together there.
Now, I still care for her, so I'm trying to find the best possible way. For example I definitely won't leave her alone before seeing her calm enough. Besides, I'll make sure her flatmate is at home when it happens, so that she can support Alice after I go, and anyway prevent her from hurting herself.
I will avoid telling her about what might be wrong with her, and focus on the fact that I have changed, and I need to recollect myself because my feelings for her are not as intense as before.
Here's my question:
If I were to prepare Alice through a longer period of time, how should I do it? It seems to me that stopping going to her apartment and remaining in a sort of limbo for days is in its own right, by contrast, something so big that might even worsen or elongate her suffering over all.
Also, I want to tell Alice that if she'll be willing, I will do whatever is in my power to help her get over this moment, and even stay friends with her when she does, if she wants to. How can I do so without running the risk of actually making it harder for her to go forward?