My wife ate some very crispy green beans after this she got a blood blister in her mouth that popped and hurt a lot doc says its herpes can this be ?

Possibly: Problems like these can only be correctly handled by her doctor in person. He/she needs to listen to her, perform an examination and possibly run labs or other tests. That's the only way he/she can find out what's going on and what to do about it.

Sure: The green beans are coincidental, especially after your md was able to visualize and render a quick diagnosis. Good luck!