Lending money to my best friend is becoming a problem

TL;DR I am essentially my best friend's only key to gas money for applying to jobs, but with no job offer in sight I can't see myself affording to have her owe me $100+

I have been best friends with her since kindergarten, about 14 years and counting (We're 19). We love each other dearly but she can be so frustrating. She is currently in very hard financial times. Her mom is struggling to find full time jobs and pay the bills. Meanwhile, my friend lives there with her boyfriend. Both have been looking for a job for almost a year. They have applied to almost every place in town and have got only a few interviews, no callbacks. It's almost amazing how incapable they are to get a job as hard as they do try.

At first she would ask me for gas money, maybe $5 or $10 here and there. I was happy to oblige, I've had no problem with her paying me back in the past. She promised as soon as she got her first paycheck, she'd pay me back.

She recently had started asking me for about $10 every week. I have a job, but my hours have been cut recently do to an influx of new employees. This last month I have spent a lot of money on birthdays, baby showers, and gas to travel to events. I'm trying to save my money for a couple other birthdays, gas to get to work, and my books in the fall.

She currently owes me $50 and I am frustrated. She has no one else to ask for money - most of our other friends are also broke. Her mom obviously has nothing to spare. Her boyfriend's dad will give them a $20 now and then, but only if they come to his house on the other side of town (and of course, they often havent the gas money.)

I am so conflicted. I want to help my friend, but there is absolutely no sign of a job for either of them in sight. How can I afford to pay them $5-$10 every single week for an indefinite time on my part time job, 15 hour-or-less wage when I have things to save for? I have talked to her about this, and she becomes extremely upset and tries to make me feel guilty, saying she has no other option. I don't think she's trying to take advantage of me, it's a fairly hellish situation. But I often find it a little hard to believe that they spend every cent of my gas money purely on traveling to turn in job apps.

What can I do, or is there anything else she can do to get a bit of gas money for the time being?