1. Never heard of CRPC, sounds like a low-bar designation to help brokers appear fiduciary (btw, how's DOL transition going for you?)
2. Even if what was recommended is legit (i.e. the discount sellers are real and plentiful enough to provide liquidity regardless of mkt vol), the OP indicated that the prospective client was elderly, risk averse, and had their emergency fund/nest egg in cash. Even if you 100% believe in your strategy and think it's ultra low risk, it would be a very hard sell for the client and would likely leave them very uncomfortable, adding stress to her life, or she wouldn't fully understand the strategy (litigation risk for you and your firm). Additionally, maybe meet with the client and determine what the target return/risk should be. Maybe putting 100% of the assets in your preferred strategy isn't necessary to meet her needs. Maybes a core of CDs w/a satellite of your ultra short munis would be a better fit.