They are similar to humans in that it can vary widely. She could start at 2 or take longer, it not unheard of for them to start as yearlings. They cycle every 21-23 days during the breeding season. The only change I notice in Vida is she gets very lovey during one phase and a little preoccupied during the next. They are all different though and some can be a little witchy.
"Until one has loved an animal, part of one's soul remains unawakened..."
- Anatole France