Ex-UCLA Star Cade McNown

Former UCLA and NFL QB Cade McNown's wife is in hot water after cops say she hatched and carried out a plan to steal hundreds of thousands of dollars in designer goods from philanthropist Sydney Holland.

Law enforcement sources tell TMZ, Christina McNown was arrested after a lengthy investigation revealed back in October she allegedly lifted Holland's purses, clothing and jewelry.

Sources connected to the investigation tell us McNown had been a trusted assistant and stylist for Holland for 12 years and had easy access to her personal belongings.

We're told Holland -- who famously dated Sumner Redstone for years -- started to notice items missing here and there over the span of several months…