1. The Sage recognizes a trick question when the Minions send one through. Assuming the husband is unaware of what is going on around him, such as not being sure who his wife even is, there is no one remaining inside to cheat on. Don't neglect him in the process, such as kicking her husband out of her bed in order to indulge her lover. However, beyond that, it is a matter of personal ethics. The Sage doubts that you, at least, have a Spiritual Advisor of your own, considering to whom you addressed your query. However, if your sweetheart does, she needs to consult this person to help her make a decision she can live with 10 years from now.
2. Lesser Advisors would suggest that you wait until after Valetine's Day, permitting a competitor to swoop in and sweep your cherished one off her feet. The Sage suspects that most girls would like a secret admirer. Where the plan tends to go awry is when the young lady decides who she believes bestowed the gift, only to express open disappointment when the true giver reveals himself. The Sage recommends that if you go through with this plan, that you permit no more than a few hours to transpire before unveiling the truth.
3. The Sage encourages you by all means to expose this mountebank immediately. This will ensure that that Alice will cut you entirely from her life, defend the man with all her being, and run away with him in order to spite you. Alternately, respect your mother's years of wisdom and familiarity with Alice, and accept her decision. It may be that Alice indulges the man's fantasies in order to add some excitement to both their lives, or even possible that like the husband in letter #1, Brian is in the throes of dementia.
4. The Sage would be remiss to permit you to continue in this manner. If you do not share this very important point with the young charmer, he will continue in his current manner for your entire relationship. The Sage suspect that even if you do, he will continue in this manner. However, losing one's early love is a far less danger than to live a life with someone whose core values appear to be so different from what you ultimately desire. The Sage would further point out that one's feelings are never "silly"; only what one does because of them may be.