She's a passable stand-up (just) but she can't act at all.
Her TV series is one of many examples of TV executives assuming that stand-up comics have acting talent. Miranda Hart can't act. Lee Mack can't act. Johnny Vegas can't act. etc, etc. Nearly all of the best TV sitcoms have starred real actors, not stand-up comics.
I would love to like Miranda, I really would but I just can't. Its all that gurning straight to camera that is the problem from me. But she was wonderful in Hyperdrive. This is one of the BBC's forgotten gems, and needs to be repeated asap, before its forgotten altogether.