@AbyssalMonkey It doesn't feel like that much of a contrivance to me since as her thought bubbles said in the last few pages the country has very limited experience with magic and in fantasy most mental control spells also make it that much harder to realise the disruption to their thought processes is unnatural. Both the Prince and his advisor noticed they were unable to meet with her but it seemed natural to them, the prince even just assumed it was the advisor getting in his way, until our probably magic disrupting Lady Lynette pointed it out. Now it'll be interesting to see if they start putting 2+2 together now they have reason to suspect the use of magic.
What is particularly interesting to me is that if we go back to the beginning https://mangadex.org/chapter/648374/2 the kingdom was founded in a place with very little magic power, of course it's possible that changed over time but it might also mean the villain has an independent source of magic power that Lynette will have to disrupt.