Of course this scenario would be quite different if she were Unflirty, but there's no nut you can't crack with a little patience and perseverance.
Something simple like Confess Attraction is all that it takes.
This will show you that the other Sim is indeed interested in yours and that a romance between them could work.
Sims can then propose marriage and eventually marry their fiancee.
In this guide to Sims, romance and love, I'll talk about the various stages of a romance and how to move your Sim one step closer to finding a boyfriend, girlfriend, or partner for life.
Use Romantic Interactions to make your Sim seem extremely irresistible and this will go over very smoothly.
It's also how you get the option to appear in the first place unless your Sim is a hopeless romantic or possibly family oriented.
Read the next section of this guide, Traits in Conversation, to learn about how those traits can make an impact.
For love, the simplest information I can provide is that Charismatic, Friendly, Flirty, and Hopeless Romantic Sims are going to have an easier time finding a girlfriend or boyfriend.
We will discuss the Dating added in The Sims 3 Generations, and how you can get Sims from going steady to proposing marriage and having a wedding.
Building Romantic Interest The first phase of romance in The Sims 3 is the Romantic Interest.
Spot another Sim who's a hopeless romantic (like one of my targets for this guide, Blair Wainwright) and they're in the bag.