I know it isn’t the whole story and like all of those music games it doesn’t measure everything but my UltraStar Deluxe (Singstar Clone) and sing practice app scores have drastically improved since I started.
Someone who probably is also willing to share his experiences with recently started vocal training is @Vik. I assume it would be more helpful for me to actually join a singing community but I just feel kind of connected to the community here. We talked about singing courses here. And since you’re composing you could do it in the range your voice feels most comfortable in.
That said I am sure you are right and she doesn’t expect you to magically serenade her with your voice if you haven’t sung before.
Would love to see her face if you do though.