How old is the GSD? At the moment, both dogs will be working out the hierarchy in your home. I'd probably need more information on the terrier's general temperament and how she is/was around you. What kind of freedoms she had and all that fun stuff. This early...I would not leave the two of them together unsupervised. Without more information on Snicker's previous temperament its also tough to say what she wants from the relationship with your terrier and how she will react if the terrier does initiate some sort of aggression.
My boy is now 3, we have a terrier in the family that is 6. My boy grew up around the terrier and would see him on a weekly basis. He's very playful and all he wants to do is play. The terrier however, is a friendly dog, but likes to be in charge/dominant. Well...for the first year of my GSD's life that was alright, he really didn't care about dominance. He turned one, and became a real dog. There have been 2 confrontations between the two of them. Both time my boy was stopped from going after the terrier after the terrier growled/snapped at him and then retreated after he realized what he got himself into. It took us a bunch of corrections on the terrier to make sure he stops growling at the GSD and finally they are just fine together. We can even leave them alone together as the terrier just ignores my boy at this point and doesn't react to anything he does.
Until you realize what their relationship will be like...I wouldn't leave them alone together. I would also not try to teach your GSD that she is lower on the family chain than the already established terrier. It can lead to various, surprising fights when the GSD does decide to maybe go up the ladder. Sadly, its due to the terrier's size that the situation can become pretty dangerous and IMO the GSD needs to be higher up in the pack order than the terrier.
CD RE TC HIC 7/10