Is it normal that my wife orgasms better watching porn and using a dildo?

When we have some cocktails and get horny sometimes my wife wants to watch porn. Her favorite position is on her knees from behind. I have a difficult time getting her to climax that way without reaching around and playing with her clit. She enjoys watching something with a big dick guy doing a girl from behind. I use the dildo which is really large and try and keep time and duplicate how he penetrates the girl. She doesn't want me talking or saying anything, likes me to stay behind her out of sight. She alway comes really hard and never touches her clit. She just holds that iPad and shudders out two orgasms in less than ten minutes.