It seems fairly obvious that she tried to defy it. After all, she knew that "a legednary SeeD" was supposed to defeat her, as when she (in Edea) faces Squall in Galbadia Garden, she says "So the time has come. You're the legendary SeeD destined to face me?"

The fact that she then goes on to try and kill him makes it quite clear, at least as far as I'm concerned, that she was defying her so-called 'destiny' at dying at the hands of Squall.

The fact that her ultimate goal is also time compression, something which would literally place her in control of time and fate itself, further backs up the notion that a main motive for Ultimecia is to battle fate itself. Ironically enough, it is her attempt to elude her fate which actually seals it.