Before getting a salt-lick, check the salt content of your rabbits' pellets (food). There's usually enough salt in there, and you don't want her to have too much, or she could get sick. It's a good idea to give apple slices as a sweet treat, because rabbits like sweets just as much as humans do
Also, if you plan on getting a second bunny, try getting a neutered male. Females tend to be territorial with each other and may fight often. I tried to introduce a new female rabbit with Whisper, my doe (does are females, bucks are males, just like in deer). They fought and I had to seperate them. Whisper gets along much better with my buck, Willow.
If you do get a casterated buck, put her in HIS cage so they can meet each other; as I said before, females are territorial and may attack him if you put him in her cage. If they seem to get along fine, then they can be put in her cage together.