The worst reason to get a second dog is as a companion for your current dog. I don't mean that as a criticism to you, at all! Most people don't realize that dogs don't NEED social fulfillment from other dogs, they need it from you. I'd be really, really willing to bet that she's not showing signs of loneliness, she's showing signs of boredom. What sort of training do you do with her? Have you considered participating in any sports, etc? This is a breed that needs much more than just play time to tire them out.
Think really, really hard about your reasons for getting a second dog. It's never a good idea unless the dog is for YOU.... saying that you want another puppy because she wears you out is a big red flag. What you'll end up with is two bored, understimulated dogs, twice the work, and twice the chaos. Focus on improving your relationship with your current dog, and if you feel that for your own fulfillment you would like a second dog, proceed only then. The general rule of thumb to follow is to hold off until your first dog is "pretty much perfect." For now, get involved in fun training with your current pup-- it'll strengthen your bond and tucker her right out