Aiya... poison her the fun of lego lorrr...

Actually can try to play lego with her. Let her build some polybag series 1st. Movie theme is the best to start becoz they know what/who is it (Batman, LOTR, Advenger). After that start to let her build some big set. Although maybe they choose the set you want, try not to talk so much and also don't comment so much of the way they build. Build wrong or they choose the set you want also nvm. Becoz the good part in Lego is you can "dismantle" it and "rebuild" it. Try to encourage her more than said her build wrong/ suck. (Now all my polybag & minifig build by my wife)

After that let her know more on Lego things. Let her know Lego is not only for children. How the adult "play" lego (MOC).

And let her know that this toy can pass to next generation. Is good to let children play lego/bricks then play Iphone .

Although my wife not so support to buy (still consider expensive toy). But so far didn't angry or turn face when I bought. Just said "Control pls, don't over spend."