Why did she cry when I offered her to go get ice cream?

She's a troubled 28 years old woman. She threatened me with a knife, I calmed her down and asked to give me the knife, which she did, and then asked her if she wanted ice cream. She started to cry, but she wanted it so we got it. Why did she cry? I try to cheer up and say inspirational quotes to her but it doesn't work...

Why did she cry when I offered her to go get ice cream?
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