Kitten and cat interactions

Hey y’all! I have had my sweet baby girl Lily for about a year now (she’s 2ish years old), and just got a male kitten (5 months old) named Misty. Lily is still wary of Misty but they play and have adapted to each other. However, starting yesterday Misty will NOT stop trying to hump Lily. Lily is not happy about it but isn’t fighting back. Is there any way to stop this? I don’t want my girl to be uncomfortable and tense in her safe space