"Mostly she just goes, 'Oh that was great, well done' and then she goes back on Tumbler, or whatever it is that they do, and talks to her mates," Metro newspaper quoted the actress as saying.
The 39-year-old said Lily treats her like a mother first and everything else come later for the teenager. "She very much sees me as her mum and the other stuff is secondary," she said.
Lily is Beckinsale's daughter with ex-partner Michael Sheen with whom she was in a relationship for eight years. The actress is currently married to director Len Wiseman.