No, Molly never finds out that Usagi Tsukino is Sailor Moon.
Molly is a close friend of Usagi's and is often unaware of Usagi's secret identity. While there are a few instances where Molly might suspect something, Usagi always manages to deflect her inquiries or keep her true identity hidden.
It's important to note that Molly's lack of knowledge is partly due to the nature of the Sailor Moon universe. In the series, Sailor Moon's identity is meant to be a secret, and only a select few people are aware of it. This creates a sense of mystery and intrigue, allowing for dramatic twists and turns in the plot.