What is that in the eye?

My mother's eye had been itching constantly for about a week. She hadn't told me about it because she thought she just had something in her eye. Now that I've taken a closer look, there is something in my mother's eye! And it's still Saturday, so she can't see the eye doctor until Monday.

Do you know what this is and how to prevent it from getting worse until my mother can see the doctor?

It's kind of yellowish, slightly translucent, on the eye, and thin? The blood vessels in the eye also look thickened, and your eye is generally red in that area or something.

I'm really worried about my mother right now. I hope it's nothing serious.