Boots first of all, the exercise routine you describe sounds adequate for a low to medium energy dog. If she is in fact a high energy dog, what you are doing for her is a drop in a bucket of what she actually needs. It is a shame this dog was adopted out to you if you are not experienced or prepared to deal with her needs. I have high energy dogs, they can run off leash for 5 hours and do it again the next day without skipping a beat. On leash walks do not tire out high energy dogs unfortunately, you could be walking her all day on leash and not notice much difference. They do need to run off leash, which is complicated by her aggression issues. I do not condone letting any dog with any aggression issues run off leash unless you have absolute perfect control and robot like recall, which it certainly does not sound like the case here.
Some things you can consider:
-buy a treadmill for her to supplement her exercise needs
-enroll in agility classes for special needs dogs (some places offer special classes for dogs with aggression issues)
-find a fenced off and secure area where you can run her, a large back yard, a tennis court if it is not in use, industrial land, a dog park during ridiculous off hours in the middle of the night when there will be no one there, get creative...
Don't feel like your dog has to have dog friends! Many dogs don't socialize well with other dogs and trying to force them into it will never improve the quality of their lives and can put other dog's safety at risk. Not all dogs want to socialize with other dogs, accept it people!! Love them for who they are not who you want them to be. Your dog can gain far more satisfaction from having a wonderful fulfilling relationship with just you and other humans.