Hey anon!
We’ve answered a few asks about getting a second dog primarily to keep your first dog company here and here. (Tl;dr don’t do it, it isn;t fair to anyone involved and will probably be more work for you in the long run).
If you’re getting a second dog because you actually want a second dog, then great! Breed suggestions will depend on who your dog gets along with. Does she prefer males or females? What play style does she prefer? Is your lifestyle better for a larger or smaller breeds?
Not trying to discourage you from getting a second dog at all! But often getting a second dog to entertain your first dog backfires. Good luck! -C