Wow! Stories like yours makes me wary of ebay (even though I still use it sparingly). I will definitely avoid this seller! I would think she would be concerned about her reputation/rating and try to resolve the issue. Even if she wasn't gonna replace the polish, that's no excuse for her response and makes me doubt her.
The polish is not primer. I wouldn't imagine that it could have leaked without leaving any residue behind
Until you get your OPI, maybe you can try a RNP base coat underneath your gel manicure. That's what I do now. I couldn't stand the long soak-offs and gritty texture of the residue left on my nails. Now, my soak off is 10 minutes max, and absolutely no gritty residue. You might have to play around with base coats to find one that works. I know orly bonder and walmart brand pro-fx: ridge filling basecoat last for me. It does not affect the life of my manicure, as long as I stop the RNP 1-2 mm from the very tip. I wear my gel 12-14 days. Revlon colorstay base didn't work so well for me. After 1 day, the gel completely separated from the Revlon, which was still attached to my nail.