Maeve can down you in just a few knives. Get Haven and Life Rip for sustain, and save In Pursuit for securing the kill. Discovery will be the best choice to keep her in check, making sure she doesn't flank from behind and poke the backlines.

Don't solely rely on In Pursuit to take her down. Use Combat Slide often to reposition yourself; it may help you avoid a Pounce. Missing could mean death, so don't jump or spamclick, as those lower your accuracy. Death Hastens is ideal against Maeve.

In Pursuit is highly effective against her. One or two shots are all it takes to let In Pursuit finish her off. Side note: She might heal while you are using In Pursuit should she have Artful Dodger, Patch Up, and/or Savagery.

Just remember that Lex has to be close to you in order to maximize his damage output, so poke from long - mid in order to have the best chance against him, because your daggers don't have a damage fall off (´・ω・`)

Lex has a scary burst damage and In Pursuit that makes it hard for Maeve to win the match up.

Get Haven and Life Rip for sustain, and take Rogue's Gambit for mobility or Artful Dodger for even more sustain. Also keep in mind Lex's Retribution; always be prepared for an ambush.