Client Preferences and Investment Decisions

Emma is a chartered financial analyst and works for a well-regarded investment firm. She manages a portfolio for a high-net-worth client, Mr. Johnson, who has explicitly stated that he prefers conservative investment strategies to preserve his capital. Recently, Emma discovered an opportunity to invest in a high-risk venture that she believes could yield significant returns. While she feels that this could benefit the portfolio in the long term, she is aware that this choice contradicts Mr. Johnson's stated preferences. Emma is trying to decide whether to proceed with the investment without informing Mr. Johnson or to keep his preferences in mind.

What should Emma do in this situation in relation to her duty to her client?