vixky,
sorry to hear of your mother. the incidence of stent thrombosis and occlusion with the medicated stents is unclear, but a problem i have observed first hand. The hope was these stents would be entrely free of these problems that have occured with other nonmedicated stents. However, the problem still exist, albeit not seemingly to the same extent.
I'm not sure where the stent is located in your mother or exactly what the rest of the cardiac history so its hard telling you specifically what your next step should be.
She should certainly make sure she is taking her aspirin and plavix after her procedure and probably lifelong. Also, she should not smoke. She is on what appears to be the right medications.