Ruriko knew Madoka was masturbating when drawing, heck witnessed it herself, buying anything other than a masturbatory device would be a bad gift. Yeah, she's an airhead after all...
Although, 26yo giving a sex toy to 17yo for a birthday... it's good there's no FBI in that universe.
Also, congratulations you played yourself.
Also, also, gave one girl from my class in HS on her 18 birthday a phallic dildo with a custom packaging with male character on it from her favourite manga...
She opened it hastily as it came in flashy expensive wrapping, bright red sparkling foil and huge ribbon...
Expressions...
Priceless.