Lucy was happy to get a new buddy, but she had a weird way of showing it, and it took her a while to get used to Molly. I blame it on a bad case of "tortitude". Even though she was more content and obviously liked having Molly around, she still liked to hiss at Molly for no apparent reason, as well as utter strangely human-sounding exasperated sighs when Molly got on her nerves. Sometimes I worried that Lucy was being too mean to Molly, but Molly kept coming back for more and they were pretty much inseparable. A few weeks ago Lucy started pinning Molly down and hissing like she was really pissed off, but at the same time she was licking Molly's ears.
Something changed recently and now it's just a non-stop licking wrestling lovefest - no more exasperated sighs or hissing. Sometimes Lucy calmly grooms Molly, but most of the time they alternate between licking, kicking/biting and chasing each other around the house and pouncing on each other. It is pretty funny. I'll be interested to see how it evolves as Molly gets older and bigger.