Al Qaeda used to have their people claim they lost their passports, in order to obtain new ones that wouldn't show entry stamps from Pakistan and Afghanistan. Those stamps, along with Abu Dabai, represent the standard terrorist routings into and out of Afghanistan/Pakistan for meetings with AQ officials, and they make for a guaranteed arrest at the US border, and at other war on terror allied borders.
But then the Embassies started getting wise to the "lost passport" ruse, and started asking questions. This could easily explain the pages torn from this lady's passport, but here's the rub. South Africa and London are not part of the standard route. Why tear those stamps from a passport? Obviously they were, as she did not have those stamps, or any others in her passport. A simple explanation would be that she tore out other, previous stamps, along with the SA and British ones, leading me to question where she was before South Africa.
If she is already part of a specific terrorist operation, she could be executing last minute meetings with her handlers, which would explain a trip out of the country and back in. She could be coming in for an operation, but if so, her method of entry indicates she is a low level "muscle" type, not a planner or leader. A leader's initial entry would be through the "front door" to keep her clean record clean. Later on she might test different entry methods, risky methods, much like Mohammed Atta did after overseas meetings while the 9/11 plot was well underway.
The point of all this is, if she is AQ connected, she is either general, non-operational "support", or else the operation she is connected with may well be in the final stages. As a leader she would have the planning well underway before needing to meet with her handlers, and if she's a muscle type, they usually don't arrive until an attack is imminent.
Why in God's name do they let the other terrorist's know when we catch one? Don't you think it might be more effective if the terrorist's thought she was still running lose and that their nefarious plan had not been partially exposed. That's my thought for what it's worth.