I don't know from your question if you are raising your granddaughter or you are referring to her lying and stealing when she visits you. Without knowing the nature or frequency of the lying or stealing I can't really offer the advice I prefer. In any event, let me offer the following suggestions: all kids, no matter what their ages, consistently misbehave for reasons. There are "goals" to their lying and stealing. These goals of misbehavior almost always fall into four categories: attention, power, revenge, and displaying inadequacy. All misbehavior stems from feeling discouraged. Teens find it especially hard to ask for the help they need. Oftentimes, the indirect way they ask for help is by doing something dramatic, like lying or stealing; if these don't work, they may "ask for help" by doing something worse.

Your granddaughter will not be helped with what is troubling her by demanding that she stop all lying and stealing or you'll throw her out. As much as you think this ultimatum might scare her into behaving properly, I'm betting it won't. It'll just show you don't love her unconditionally, which she probably feels anyway and it will push her into having to one-up you with her response.

I strongly suggest that you say something like, "I obviously don't understand what's causing you so much hurt inside. I know you don't feel good about stealing and lying and I want to help you feel better. I'm going to make some calls and find out the names of a few therapists who you could trust and you can interview them to see which one you want to work with. I'll support you in any way I can so that you can feel better about yourself. I know it's tough being a teenager these days but I can't sit by and see you do things that show such disrespect for yourself. Our deal is that I'll try to get you the help you need if you promise to work hard to help yourself. I know you can do it!"

Forgive her grandmother and become her champion if she'll let you. Good luck.