Use 'reliant' to describe someone's need for assistance from a person, group, or system. She is reliant on her parents for financial support.
Pro Tip 2/3
Vulnerability
'Reliant' can suggest a weakness or disadvantage if the support is taken away. The village is reliant on the old dam, which is concerning.
Pro Tip 3/3
Not Interchangeable
Don't confuse 'reliant' with 'reliable.' 'Reliant' means needing support; 'reliable' means providing it. They're reliant on a reliable transportation system.