What are some signs to look for in people who are suicidal?

My neighbour committed suicide 10 days ago by jumping off a cliff and I feel so very sad about it and wondered if there were signs that I didn’t see.The police found a suicide note in her apartment. I knew she suffered from depression and was struggling with her mortgage payments and she gave away her 2 dogs last month, perhaps I should have questioned this further. She was only in her 30’s. I have known her for 8 years and we would have a chat and a coffee in each other’s apartment over the years. I am still in shock and can’t stop thinking about her. Has anyone else ever gone through this?