Well,Fiora is a hard match up to play with Lillia, but it is still possible. Try to avoid Fiora´s passive resetting it (losing vision and then come again, always trying to have the mark behind you)
You can poke Fiora a lot with the Q, and also, Lillia have better wave clear, so you can push her into torret.

At level 6, Fiora´s W can avoid Lillia´s R, so you need to make her to use the W before. This let you to make the combo better.

Probably Fiora need to rush the Mercury boots,so don´t despair if you don´t make a lot of damage, it is normal.

Above of phase of lines, Lillia has better TeamFight, your intention is to "feed" your allies, because Lillia takes a lot to destroy towers. Fiora will be probably splitpushing, you can try to defend the tower, but is better for you and the team to be with them

Probably Lillia is going to have a nerf in Q and W damage, but until that, i think so