Your ex-fiancee is absolutely on the ball...yes you can develop 'cold
sores' sans sexual relations.
All Herpetic infections are not sexually transmitted.
Earlier there was a notion that HSV2 was sexually transmitted & affected the genitalia & HSV1
appeared on the lips & was non-sexually transmitted but with the sexual practices having changed worldwide, this does not hold true anymore.
One can do a serum (blood) IgG
& IgM test to figure out the titres & type of HSV & this will give you a clue. Besides it will tell you recent infection or old infection
Wish you both good health! Cheers!
Dr Praveen Rodrigues MD