The Swiss were willing to resist anybody that invaded. There is zero reason for the Western Allies to invade. They need all their resources to deal with Germany, Switzerland is no threat. If at some point they want to "punish" Switzerland, they can do that after they defeat Germany. At that point they literally surround Switzerland, and can control what does or does not enter the country which will bring the Swiss around with no bloodshed.
As far as imprisoning Allied pilots who end up in Switzerland, interning combatants who end up on neutral soil is part and parcel of normal rules. OTL the RUSSIANS interned American aircrew who landed in Russia after bombing Japan, as even though the USA and Russia were allies, Russia was neutral with Japan - although the aircrew eventually "escaped". "Financing" by a neutral of one or both combatants is perfectly legitimate, in WWI the USA had loans to both sides early on, later only the Entente, and of course in WWII the USA had loans to Britain and France while still neutral. Assisiting the Nazis in hiding the loot from the Jews and others is another story, but very little has ever been done about that OTL.