This is the same as "Eat right for your blood type" and it has gone in and out of fashion. I am also blood group A, and according to the original version I'm not supposed to eat meat - but with being iron deficient and already avoiding the foods I'm allergic to, I didn't think I could take it on. When you go through diets like this there are often other factors that may be the reason they work - e.g. Is it because it's low in sugar or fat, low in animal products, only allows meals to be made from scratch with nothing from a packet or jar? Some blood groups are told not to eat wheat - and yet there's a variety of reasons why that may make someone feel better (and none of them can be proven to be related to blood group).
This is one of those things that doesn't have the science behind it - and yet it thrives because enough people feel good on it. There's certainly no harm in you trying it - so long as you aren't already anaemic like me and the diet requires you to remove the best sources of iron. Don't forget that if you're on acid suppressing drugs, iron from non meat sources is very poorly absorbed (it can't be extracted from the food).
Look at the diet carefully and ask yourself what else is it - is it low fat, vegetarian, gluten free? Have a look and be aware that those other factors may be contributing to any benefit. That said, if you're willing to give it a go, then do it for a couple of weeks, keep a symptom diary and report back! There is no single one size fits all solution - who knows, this may be your thing!
New stuff: GERD. Interstitial Cystitis
Lifelong stuff: Food allergies, eczema, asthma