I'd say continue but there will come a time when you feel you need a teacher it may be that you've reached that point - are their any yoga teachers at all in your area? If you're interested in one style it can be difficult but at least if you get to a yoga class your instructor can check your alignment and what you are doing safely, what you work on at home or with your friend is up to you, perhaps your yoga teacher will know someone who can help.
If there is no one at all that's tricky. You many have to save up and travel to workshops or weekend retreats or even private instruction.