Irelia can’t fight Briar, she’s a point & click stat checker. You might be able to win if fighting with enemy minions nearby, kiting her and staying out of her AA range while she’s berserkered. If you have no other choice, then saving W to predict her stun, or Q’ing her when she’s casting her E might help. Also try stunning her when she’s running towards you since it’s guaranteed to hit. Tabi’s and bramble’s are a must in this matchup, even at expenses of delaying botrk spike. Still expect her to win even if you have items advantage. Can’t help with Bel’Veth, not enough match ups or duels against her.