I hope by now you have been able to get help for your friend and that everything is ok.
In the event you still require assistance - following are some links that might be of some help. Keep in mind if your friend does not have quality medical/travel insurance all options are going to require significant cost and I hope that family & friends will be able to assist you with this if you do not have access to funds required.
My personal advice (I have no medical background) would be to first seek medical advice in Bali - personally, I would not have any surgical procedure in Bali unless it was an immediate and life threatening situation and there were absolutely no other options available to me. If circumstances allowed the time I would seek two opinions. The following would be my personal first two choices for critical medical advice in Bali:
BIMC hospital would be my first option for advice:
BIMC Hospital – Bali – 24 Hour Medical and Emergency Centre
Prima Medika is a private hospital in Denpesar where I have received excellent care and diagnosis when my father had a stroke - I need to stress that his condition did not require surgery:
Prima Medika Hospital - Home
After receiving first and immediate advice from the above facilities in Bali. If circumstances required and permitted travelling for any necessary procedures I would consider the following regional centers for further advice and procedures.
Singapore - I have never needed to seek serious medical assistance in Singapore however it is the closest major center that offers quality medical/hospital facilities.
BIMC in Bali should be able to refer you to a suitable facility in Singapore (or perhaps ask around for further advice on Singapore hospitals).
Bangkok - Is a little further but has got an excellent hospital Bumrungrad. Again, I haven't needed their services but have had many friends that have had first hand good experience with the hospital. I have visited friends in this hospital and I was impressed with it's facilities and service. It is only a guess but it may be less expensive than options in Singapore.
Bumrungrad International Hospital | World-class Bangkok Hospital in Thailand for Medical Tourism
Perth, Australia is also only a few hours flight from Bali. Australia is the closest country with a public health system which has reciprocal agreements with several European countries. However I don't think Germany has an agreement with Australia and the medical emergency must arise while you are in Australia - so it will likely be of little help. For more information:
Visitors to Australia - Medicare Australia