[Sendric]

Adding a lycanthrope template is like starting off with a monster race. The number of hit dice and the level adjustment change her effective character level. Your example of a 1st level character afflicted with lycanthropy (weretiger) becomes a 9th level character (1 class level, 6 racial HD, +2 LA). Assuming you don't want her to be a 9th level character, there is a way to slowly introduce the racial levels. Savage Species has examples of how to do this, but basically you would level her with racial hit dice instead of class levels for 8 levels.

I did this for a character in my campaign (werepanther), so if you're stuck on how to begin, I can throw some ideas your way. As for HeroLab, the template is currently configured to add all levels at one time. If you want to do it one level at a time, I imagine you would need to create a new class called weretiger, make it max out at 6 levels, and have it progress as a class would (but with the weretiger features). Somehow we'd also have to introduce a level adjustment, but I think that might be possible through an eval script.