Sorry, but I don't think I am understanding the question properly. You can't command an inactive sim to find your sim attractive, they either do or they don't by way of the game's attraction formula and its the associated positive factors or penalties that can be worked on. A lot of ingredients go into that including but not limited to matching or compatible traits, certain LTRs, money, celebrity levels, zodiac signs, friendly relationship scores and how much they know about each other, gender preferences, whether both sims are single or in relationships, an element of randomness, short term things like hygiene and mood, etc. What we can do is use the Scan Room feature that Woohooer provides on the active sim when in the same room as others, with the understanding that the resulting scores will always be bi-directional (mutual).

Some sims just by their nature and traits are more flirty than others.

Also what we can do is break down some of the barriers to autonomous flirtations and other such behavior once another sim finds yours attractive, but those kinds of settings are going to affect all sims in the world and not one particular couple.