I posted this vid earlier, it supports your theory, but doesn't prove it. Some are reporting that Ana was involved with the deal all the way up to her death. Then Brian finished sale days after. #AnaWalshe #BrianWalshe  

#BrianWalshe arrested May 9, 2018. Ana with bruise on her face May 21, 2018. 12 days after Brian arrested by FBI, Ana who was harassed by art dealer he robbed, may have confronted him? She posted #vulnerability on her pic. #AnaWalsheMissing #AnaW