At the outset, please ask your girlfriend to stop 'squeezing' this lesion. Am sure her talents could be put to better use elsewhere.
What you describe is most likely a sebaceous cyst
that has possibly been secondarily infected.
Squeezing will probably only serve to rupture the follicle & leave a dark ugly mark in its aftermath.
Your best bet would be to go across to your nearest dermatologist
or surgeon & have him take a look at it. Most likely it will have to be 'surgically' excised in toto.
Dont worry it is a small Outpatient procedure, easily done under local anaesthesia.
Cheers & wish you continued good health !
Dr Praveen Rodrigues MD