Ada looks sixty if she’s a day. In actual fact if she drops the spell that maintains her appearance, she looks young enough to be her son’s daughter. As a fae, she can control her ageing – even when she’s in her advanced years (300 or so) she can make herself look as young as a nymph.
Not so in the mortal realm. On a busy street like The Terrace people notice if you don’t age. That’s why it takes her so long to answer the door; she’s quite literally putting on her face – that of a sexagenarian.