it is great that you want to encourage your wife and she is happily on her way, but there is no such thing as a beginner kiln. they come in so many varieties to suit different needs she may need to discover what will work best for her before any purchase. we have had several spirited discussions on this subject in the last few months.
you might consult some of the books on ceramics and pottery to be found in your local library. since your wife is interested in the field and wants to continue, she will want a kiln that will handle the work that she will produce. installing a heavier circuit will be a necessary step. you might find a used kiln to reduce the total costs if that is a consideration. visiting several potters to see what they produce and how they fire their work might help you both know more about what to buy.