Concern?

[Juliet51]

Should I be worried about a friend?
She has become vegan. She eats the same thing every day which is
Porridge and banana for breakfast
Falafel for lunch. I don't know if anything else is eaten with the falafel?
Nuts (cashew or peanuts) for dinner.
I am concerned about this. Am I right to be concerned? If you agree, what can I do?

It does sound restrictive and in any case, eating the same foods and meals day in and day out is definitely not healthy, we all need variety.
You could try asking her if she's okay in herself and let her know you are there for her if she needs to talk. Often eating disorders aren't so much about the food, they are about trying to feel in control of life and often there are symptoms of underlying depression/ anxiety/ low self esteem that can contribute. You sound like a good friend, keep checking in with your friend, that's all you can do.

I'd be concerned too although not sure what you could do.