Her WP path is bad, or at least not as good as her cp path. This is for 2 main reasons:
Her A: for you to stun you need to stop attacking, which as a WP carry is not something you like to do. It reduces your DPS and makes you useless for 1.2s (maxed).
Her B: it risks your positioning, and unlike CP Ylva, you will waste either the speed boost (to take advantage of your attack speed) or your attack speed boost (to use the speed one to reposition), either way you are wasting one of the buffs, and the fact that you are in a bad position will reduce your DPS if you decide to scale or will kill you if you decide to scape.
She is bad in 3v3, her laning phase is none existent, there is no reason to use her, she is just a far worse ringo (WP) and her CP side is horrible in lane.
As a jungler, her farming is bad, and she is extremely vulnerable to the other junglers. Also her ganking potential isn’t that good, specially when the roam is in lane. In a meta were snowballing jungle is key, she is just weak, doesn’t have presence in jungle. Her burst (CP) early to mid is good when she comboes her B, but in late game she is a joke. There aren’t that many places to put a sneaky trap, so her C is basically useless in the mode.
In general, I don’t think she needs a buff at all, she has enough damage, but her kit just isn’t good in the mode.
If I was gonna use her, she is specially good against melee laners that can’t be out of range from the bushes, other than that there is no reason to actually use her, maybe against squishy junglers?
No, better not pick her. If you enjoy her, you can make her work, it isn’t like she is useless, she is viable, but not meta. If you pick her first, you are calling for a reim or GJ (which are both top tier) and you will lose your jungle.
Mainly melee laners that can’t stay out of range from the bushes. Sadly it’s very easy to ping her down when she dives and the laner usually builds SH, which negates completely her damage, and she has no reliable scape.
All meta junglers are better than her, and her job as an assassin is better achieved by Anka, koshka, BF, GJ… as I said, apart from you enjoying her, there is no reason to pick her.