My 8 week puppy has just started exploring the garden and seems to be very interested in the weeds that are growing up through the patio.  She biting away at them all the time, I'm not sure if she's eating any of them or just playing and pulling them?  Is this normal or should I actively stop her?

She's also obsessed with the flowers from my fushia bush!!

im not sure if this is normal behaviour but i dont think you should allow her to chew plants and weeds as some plants and weeds are poisonous to dogs

Very normal, pups explore everything like babies by putting it in their mouths, even more so as they so not have hands, but of course some plants are poisonous, and there are lost of lists on line.