I think you probably answered part of your own question by saying "the second sentence doesn't lack anything". Logically, "doesn't lack anything" must mean "has something" (i.e. has a subject).
In the television example, "the time spent with television personalities". I think time itself is a subject, but it is not a physical location, so using "where" is not correct.
In the theatre example, the "subject" is a physical location (i.e. the theatre), where she worked. So using "where" is correct.
However, English is such a fuzzy language, exceptions exist and they may not be "proper grammar". For example, "In the time where people and machines come together...". It should be "In the time when ....". But in normal speech you can hear this sometimes, and no one seems to bother about correcting it.