I feel like this is something I can talk about a bit. Lylyth3 is a worse version of Vayl2. I have said it before now I am going to say it again. I do not like Lylyth3. I do not think she fits into a 2 list pairing.
So lets get this out of the way.
She is a shooting denial caster. That sounds strong in the current meta problem is that her denial does not work. She does have a hit buff, that is her feat, meh, she got no damage buff. She got nothing. She got her own personal work but guess what so does Vayl2.
She's a fury five caster. With an important three cost spell. Since she does not really want to be up in the fray she got a 1 cost animus for snipe. But wait she got Blood Boon to use her important spell. Just that the spell stops her from shooting more and her attacks are no longer simultaneous so if she kills a infantry model on the second shot do you really want to wait until the third shot to put up wind wall. You might miss/not pop armor. This is a small skornergy but it is there.
You know what other caster puts out 3 Rat 8 pow 12:s. Vayl2 does. Vayl2 is further away though. With longer range. A better ability to boost. Does not have a huge base, so does not need to camp as much and can have stealth. Wait this was not a Vayl2 article. Oh well.
Then lets look at her shooting denial, wind wall. All ranged attack miss unless they have magical weapon. That is great unless for the part where it does not work against anything. All retributions jacks got magical guns. The conquest does not care if it hits. Pow 10:s are good enough to ding her up, especially if you ever have the bad luck to face of against pButcher double conquest. Then she just dies on the feat turn. Kara Sloan will not be dropped into it unless they play Stormwall and Arlan just since then they laugh at this matchup. Caine2 players do not care and laugh all the way to the bank. Haley2 players out threat you with a real alpha. Shit is sad. Mercs don't pay Lady Aiyanna tax, so they always bring her and got a good colossal.
Then we have her order of activation problem. If she actually is in a good matchup she has to activate last. Since she wants wind wall and then your shooting army can not shoot at him. So all the other stuff needs to shoot first. That create problems when you want to feat, heal or pass out wraith bane to models in your shooting army.
Her assassination. This is supposed to be her good part. She can stationary a caster. put 3 pow 12:s with boosted damage. So who the fuck cares about that? Oh she can follow up with other guns. Well no. Your opponent does not suck so you wont get any other guns. Camping 2 focus is usually enough for someone to camp through this assassination. For Vayl2 that number is 4 focus instead.
Then look at Vayl2. She gets 2-3 pow 12 and a pow 13 all with boosted damage. At a longer range.I see no reason to play Lylyth3. She can be some use as a detergent from non stormwall Sloan lists. Still do not see that as good enough to use 1/2 list to just screw with your opponent. Not right now at least. Back in the old Vayl2 days it was okay now you need more from your lists.