your girlfriend should see a health care professional about this. it's not the kind of thing you should try lancing yourself as that can introduce infection into the wound and cause more problems. your description of the lesion makes it difficult to tell if it is a bartholin gland cyst though it doesn't sound like it. these types of cysts occur very close to the vaginal opening. like i say your girlfriend needs to see a medical professional about this. wishing you well!
my girlfriend has an egg-shaped cyst or boil near her pelvic bone. it is very hard and painful. can it be a bartholin? . we placed a small incision and got a little infection out but it is still very painful and almost the size of an egg. it has a line going to the swollen area almost like it is a vein or artery feeding it.