[She hasn't been in the best place the last few days - her son returned home to Kiseki, and now her daughter's been put into a magical suspended sleep - so she hasn't felt as cheerful as she might normally. Still, she's not one to ignore someone who's just arrived and seems confused... even if she's familiar enough with Arthur and Merlin to understand that this seems slightly off from how she's heard of Morgana]
You don't have to worry. [Relatively speaking] Arthur and Merlin are both here, and I'm sure they'll be able to explain the situation to you.