Star Trek: 10 Things You Didn't Know About Guinan
7. Guinan Lies
Guinan herself is not a time traveller. Rather, she is a being who, for the most part at least, doesn't feel the same effects of the passage of time that other corporeal beings do. However, this has brought her into conflict with some who chose to take shortcuts.
In this example, Guinan was forced to conceal the details of Picard's journey back to the 21st Century. The pair met - for a second time, from Guinan's point of view - when the former appeared in her bar in LA. This kicked off a set of events that, eventually, saw Captain Cristóbal Rios remain in the past.
When Picard et al. returned to the 25th Century, he finally noticed a photograph adorning Guinan's wall - that of Rios, and Teresa, safe and happy. This, Guinan noted, was technically a spoiler, though innocuous enough that no one ever really noticed.
The rules of time travel tend to vary from person to person, but Guinan seems to hold on to that addage - no spoilers, sweetie!