What do I do? (Friend problem)?

One of my close friends has been dating this guy for like 2 months. They are very very touchy. At school (I am in high school) she is always hanging on him. They will stand hugging for long periods of time and when they are holding hands she will lean into him. I hardly see them apart and they are always kissing! When I try to talk to them at school it is so awkward because there continuing PDA leaves me feeling very 3rd wheelish. At lunch today they were expecially touchy. My other friends and I have talked to her multiple times about how their PDA makes us feel uncomfortable and other people will soon start getting a bad impression of her. She says that they have no time outside of school to properly date and I understand but it is getting ridiculus. Now if someone tries to talk to her she gets upset and says she can't help it. What do I do?