I am the younger of two daughters and worked since high school. My older sister, because of her situations, resulted in my parents paying for and caring for almost every aspect of her life. She grew-up to be a dependent adult. My mom justified it by saying that my sister needed the help and I didn't. What it did was create an environment that developed a co-dependent adult. So, instead of helping her become more independent, they did things that encouraged co-dependency.
I believe this "entitlement" belief follows her until today as a woman with a family of her own. She is raising her two boys to be co-dependent as well telling her husband that, "my parents never made me pay for things so I don't think we should make them pay for things." Now she has an 18 year old living at home without a job...for the last job she had, she quit for him - called his boss and quit for him. Ugh. Her husband used to call me to complain about her spending, lack of control, way she teaches the children - I told him to stop telling me these things because it puts me in an awkward situation and plus he isn't doing anything about it.
On the other hand, I worked since I was 16, I paid my way through college, lived on my own since high school and am completely independent from my parents. I put both of my son's on an allowance with a list of jobs they could do to earn more money. I never buy toys for them on a whim - only for events, like birthdays. It is expected that they purchase their own toys. Now, they save their allowance, mind their wallets, count the money inside, have bank accounts, have piggy banks for coins. And they are 7 and 4 years old.
I kept hoping that one day my parents would cut the purse strings for my sister because it would teach her many great lessons about money and self-sufficiency.
In my very humble opinion, I suggest you put her on a budget. Give her an allowance appropriate for her age level and stick to your guns. The rest must come from her own ability to earn money. It is an important life lesson that she may not appreciate until much later in life. It is the right thing for her and also the right thing for the rest of your children who clearly see her dependency on you. They may not say anything, however, know that they see this as well and may be secretly hoping you'd do something about it one of these days.
She can find the time to earn money. She'll need to sacrifice other activities to carve out the time to earn money. It sucks, but it is life.