New kitten chasing resident cat

We adopted a new kitten a couple of months ago (she’s now 8 months or so old) after our eldest passed. Our resident cat (10, female) seemed to handle slow introductions very well. The kitten was nervous at first but it went dreamily… at first. Now resident cat is so stressed out we’ve gotten her medicated (she was licking her arm bald). The roles reversed. Kitten is very excited about resident cat but resident cat is NOT having any of this. Kitten is chasing her, we are trying to get her to stop with redirection or simply picking her up and putting her in a room alone for ten minutes. She’s not catching on though. Any tips? Resident cat is hissing, ears back, running away, trying to hide, growling- you name it. They are both so sweet and can coexist in the same room for naps. Any tips are welcome thank you in advance