It seems to me that there must be some rational or reasonable balance though.
Yes, she chose to date the potential future King, so unless her head is filled with sawdust, she knew it wasn't going to be a very private relationship. She certainly must have known that to continue that relationship after St. Andrews it would become even more public, as the Prince's period of relative privacy would be coming to an end. He knew that, he surely shared that information with her, and they made a decision to carry on together. However, the extent to which she appears to be hounded, and I do mean hounded, is ridiculous. We don't need to see her come and go at every hour of every day, and dating William does not automatically equate to relinquishing her basic human rights.
There must be a fine line somewhere of what's a reasonable amount of coverage without treating her (or anyone else, for that matter) like an animal in a cage. We just don't seem to be very good at finding that line and staying on the safe side of it.