Could my gf transmited herpes to me ? she got cold sore on her lips after 25 days i made a blood test it came igg +ve igm -ve

Not likely: It sounds like you had hsv before; 25 days is too short to make a full transition between igg and igm, you would expect at least some igm present.

Herpes: Herpes is a pain since it can be transmitted even when there are no active sores. A positive igg means a previous infection or exposure. The igm shows that there is no acute infection.