Your lawyer sounds a little wacky, to be honest. I don't see how withdrawing the money into
cash and waiting for three months would change the fact that you still own the money and that she's entitled to some of it in case of a divorce. Maybe there is some quirky local law, though.
The typical approach to this would be to move the money into something like a trust or foundation, thereby legally separating yourself from the money. The biggest caveat is you need to do so in good faith and not for the purpose of preventing a known event, i.e. you can't do it if have been served divorce papers or if you reasonably should have expected a divorce within a period of between one and three years prior to setting up the trust/foundation. The duration varies between jurisdictions and is called fraudulent conveyance.
Cook Islands, US, Samoa, Switzerland, Liechtenstein, Mauritius, and Panama are all interesting and generally well understood jurisdictions for these types of arrangements.
Discuss your situation with fiduciaries to see what the duration of fraudulent conveyance would be in your circumstance. Also make sure you are compliant with local laws where you live.