Some females may never lay eggs. Some may not lay their first egg until they are well into their teens or even early twenties!
How often? Well, she could lay 2-3 eggs, every 2-3 or so days.... or maybe it's the only egg? Maybe she'll lay another in a week or a months time? It's hard to say!
One thing is for sure though.... if there are triggers to egg laying, then there is a higher chance of egg laying to occur.