Using Vector math is the best solution. You can get the direction of the by using the getlookAtRotation and rotating the AI’s forward vector (Not location or rotation) by that amount (essentially saying that this is the direction of the player relative to me.
From there you can use a cross product to find out what direction is 90 degrees from there. You could also use the dot product and some logic on the result. There are examples Herein cpp but it’s just math and results so it works in blueprints by plugging in values to nodes.
That will help give you a direction and then you can use the same types of checks (maybe with a random unit vector in cone of the inverse of the direction and a 40 degree cone to get the flee direction.