Wood release is the kekkai genkai of the Senju clan (originally the God trees sacred ability and also the Otsutsuki clans Kekkai Genkai), however, Moegi is able to do it by combining Water and earth style. Does this mean being able to combine 2 elements can allow anyone to use an advanced element? We know Orochimaru used to perform experiments on merging Hashirama's cells with small children but Sarutobi Hiruzren (the Third Hokage) put an end to it.
Moegi did not have the wood style ability while she was younger plus the experiments that Orochimaru did with Hashirama's DNA were destroyed earlier in the series. So how did Moegi suddenly become able to use it at adulthood?