My cat has been attacked

Hi, I was wondering if anyone could offer up any advice for me? Recently, my cat (who goes out regularly as she pleases, however her only way of getting in and out is through the front door so whenever someone needs to come in/come out she does as well, if that makes sense) came into my room about a week ago, stinking of urine, covered in mud and licking a small wound on her stomach. We examined it and it didn’t look deep, it wasn’t bleeding so it wasn’t enough of a problem to go to the vet, especially as the vet is incredibly expensive. Last night, she came home again, smelling of urine and slightly sour? And she has a wound by her ear, not that deep but it was bleeding. We are taking her to the vet tonight, but I was wondering if anyone had a similar experience and any advice they could give for me? I’m just so worried about her going outside again in the future, this has happened twice now and I’m so scared one day she’s going to go out and wont come back. I talked to my dad about it and he said that we can’t really stop her from going out but if anyone had any advice I would appreciate it so much.