Women are always horny. The down "cycle" you describe is her inner struggle to not be a horny slut, because society says that's bad. The dam then breaks and she starts around talking about porn star sex before the guilt drives her, again, to a no-sex cycle.
The up cycle comes whenever you make her feel bad for not putting out, such as sitting in a chair, scratching your balls, drinking wine out of a box and loudly declaring your cycle theory, full of pregnant pauses and suggestive glares.