firstly, I would suggest you sound her out.
To steal takes alot of courage and she must be quite troubled to do
it.
Why not try to understand her first? And see whether you can help
her.
Cause if you push her hard, you won't know where & what she
will do in future.
And most importantly, you lose a chance to have a rapport or a
chance to communicate with her.
One thing missing in family is communication. If you don't
communicate, your family members will find people who communicate,
and there are many people out there who loves to communicate, and
then may take them down a different path.
Just spend time, talk to her nicely and try to understand her
needs.
And if you do communicate with her, and she wishes it to be a
secret. You may consult your parents depending on the gravity of
the situation.
cause ultimately, you are still family. blood is still thicker than
water...
