You might want to get over that mindset that attitude towards sex is the only factor that matters in whether people want to spend time together.
Like mentioned previously, Lena likes to spend time with Holly because Holly is a writer she admires, and they share quite a few personal experiences, like their family situations. Lena isn't some sort of brain-dead zombie who only thinks of fucking 24/7, she has other interests, ones that happen to intersect with Holly, regardless of what either of them thinks about sex.
And Ivy spends time with Holly because, aside from other factors, Holly is Lena's friend, and Ivy doesn't want to be excluded from Lena's social life.