Oh my gosh, I am so very VERY sorry. This is hard to read. I hear your sadness, your regret and your pain. Please know that she must have been dealing with so much for her to have taken her life by suicide. You brought her joy. To do for others makes many so happy. To love someone. She loved you. She knew that you loved her, don't doubt that.
I agree that perhaps her health was taking a turn for the worse and you weren't aware.But those who think about suicide usually are hurting terribly emotionally. She's not suffering any more.
I am so glad you that you are starting therapy. I personally went through a painful loss of someone I deeply loved that died unexpectedly, tragically. Therapy helped me very much. Staying busy and distracted. This is a lot for you to deal with. She doesn't want you to suffer so do what is necessary for yourself to get through this. I'm thinking of you.
I am so, so very sorry about Alice.
Suicide is never someone else's fault. Obviously, she'd had a lot happening in such a short time, and perhaps she found out that the colon mass was malignant, and decided she was done fighting with her body.
She chose to express her love for you in the way she did, and that wasn't conditional on how you received it. I hope you can just be grateful for that. She knew who you were, and what your lifestyle is, and decided that you were worthy of her love. If she needed a man to be there for her daily, she'd have chosen someone else.
I hope your memories will bring you comfort. I'm sure you brought more to her than you realize right now.
I don't know all that happened, obviously, but I kind of have developed my own way of looking at this kind of thing. My Mom got cancer when I was 17, and ended up paralyzed from the waist down. It drained her of her joy and drained my Dad of his spark as well. She stayed pretty much the same, with the same amount of pain, for 7 years, and then ended up in the hospital and basically starved to death while on morphine. My view was, the death wasn't sad. Her drained life and the illness were what was sad. We all die at some point, so it's the life while lived that's most important, and in this case, she was quite sick and obviously decided this wasn't how she wanted to live the rest of her life. That doesn't at all mean she didn't care for you deeply or that you didn't do for her exactly what she needed, it's that you couldn't give her what she needed, which was health and a future that wasn't going to be filled with medical procedures and pain. It's not at all on you. Like you, I'm not a believer in the afterlife, but if there is one, she's got a chance to have a better time of it and if there isn't, she's completely free of all that ailed her. Grief isn't a mental illness. It will take time for this to mitigate, and it may never completely go away. But don't measure the death, measure the life, and it sounds like you two had a wonderful time when you were together. That says it all. Peace.