How do you tell someone who is like a sister to you that she is taking advantage of you?

Ok a little back story

By best friend is like a sister to me she is divorcing her husband they still live together until she can afford her own place. He is taking her old car and she is getting the new car.

Last week he popped a tire in the old car and they hadn't gotten around to replacing the back up tire. Last Saturday she was hit by a drunk driver. She's lucky to be alive cause it was the drivers side back door.

Drunk driver has no insurance and is in jail for a dui and having meth on him.

Neither of them have very much money until next payday (idk when that is)

Her car is in the shop waiting on parts since her insurance covers this.

She bought a tire to put on the old spare tire rim but that popped too cause her ex somehow fucked up that rim too.

Now on to my issue. I have one working car as we wait for our own payday to fix the other. I have 4 kids. Two of which are sick and a 3 month old who has yet to get sick. She keeps borrowing my car to run her taxi company and take her ex to work and pick him up, at 5 IN THE FREAKING MORNING!!! Or she asks my husband to take him to work and pick him up. This means my husband loses sleep. And we waste gas we desperately need. And when she borrows the car she doesn't bring it back until I ask for it or if I wait she uses it for her errands and doesn't bother to ask if I need it. Remember I have sick kids and a ticking time bomb of a baby who may get sick and get a really high fever in which case I would need to take her rod the er and I can't wait around for someone to take her sweet time returning MY CAR!

I'm sick and tired of this. It's not like I'm the only friend who has a car. I'm just closest. And a push over apparently.

Idk how to tell her she's fucked cause I need my car in case of an emergency without sounding like a selfish bitch.

Idk am I being a bitch? I get this is a hard time for her but I have a family to care for, food to buy and errands to run. And I can't do that without my car.

Could this be dry semen?