How do you know it as HER blackberry? She might have borrowed it from a friend.
Alternately, it was one item she had left over from her previous life, before she ended up homeless. It's not like Blackberry's have much resale value. And the monthly fees are not huge if you get a basic plan - it may be cheaper than scraping together first and last months rent, just so she can put in a home phone, and then pay monthly on THAT. When people are living hand to mouth it's hard to convince them to put their pennies in the bank. For what? So she can have no phone for a year or more, while she tries to raise all that money?
Or she bought it super cheap "off the back of a truck", as it were.
When people have so little, I really try not to judge them for the things they do have.