So it really boils down to as why Aidra keep it all to herself.
Was it just a pure, honest, motherly intent to not involve the person she admired (Bard) and loved (Joulran) the most in any political shenanigans? If so, why left seal on Bard secretly? I suppose when things when to shit, she wanted to make sure that the truth is in the right hands.
But then, she confided with the maid, didn't she? I suppose one never really planned for the maid to even converse with Bard about exactly that topic, so it was truly the only venting coping way she has over the whole matter.