It is unfortunate that you were given the advice that you were provided. Without question, the best option for you would be "pre-surgical" orthodontics (not purely corrective orthodontics), done in conjunction with an orthognathic surgeon. You are young and the process is definitely costly, but I would consider this option. You should probably start with another orthodontic and/orthognathic surgery opinion. Good luck to you.
Unfortunately, the orthodontist is incorrect and it is common for some of them to 'try to help out' by using 'orthodontics only. They do not have the same regard for the facial balance in some cases and the long term effects cosmetically. (eg looks less ideal as you get older due to soft tissue changes like double chin etc).
I would recommend you see an Oral/Maxillofacial surgeon and have him direct the orthodontist now, before your lower teeth are tilted too far forward, which is hard to reverse.
The lower jaw surgery can be properly explained to you; rather than 'scare you' as you have noted