Should she turn down being her friend’s maid of honor?

“My friend who I have known more than half my life and is basically a sister to me is getting married. She has asked me to be her maid of honor, and even though I 100% support her and her marriage, I don’t think I can do it.
I get terrible anxiety and the pressure of it, the speech and everything else is overwhelming. I don’t want to let her down. What should I do?”