I’m sorry for your loss.
My aunt (who was more like a big sister, we were only 5 years apart) recently took her life. It has been a couple months, but the entire family just had no idea she was going through anything and we are all stunned. The lack of answers is probably the hardest part, at least for me, trying to assign some logic or reason to why she did this.
Besides going on about myself I wanted to make sure to mention this book that was helpful for me. Perhaps it will help you. My thoughts are with you.