Mixing is even dangerous for pious people with good intentions. It is not a rule that is meant only to disarm those with bad intentions. It is meant to make things easier for people with good intentions by taking away opportunities of temptation. SO even if it is only with good intentions, don't do it.
I remember this story, three brothers have to go to war and they have a sister but noone to take care of her. So they ask an old man which is very pious if he cold look after her. First the old man refuses because he is afraid of getting tempted. But after a while he thinks, well it's with good intention only to help them out, so it should be ok. He lives in a tower in the upper rooms and gives the sister a room al the way down. Three times a day he comes down with food places it in the halway, quickly runs upstairs and yells that diner is sevred while he is halfway up the stairs so that by the time she opens the door he is already upstairs. After a while he thinks, maybe it's better to place it on her doorstep so she doesn't have to come outside. That would be easier, she wouldn't have to come outside, but only open the door and take the food in. He also gives her some books to read because he thinks she will get very lonely and bored in her room. After a while he starts thinking maybe I should try give her dinner without running and yelling she must get so lonly and the only voice she ever hears is me yelling so I should try not to yell. So he places it at the doorstep and alerts her of the food and then walks up his stairs. After she has read most of his books he thinks she must by now be really lonely maybe I should talk to her just a lil bit from the other side of the door. Just ask if everything's ok and if she's doing alright. After a while he starts to think everytime she opens the door to take the food people passing on the street can see her so maybe I should open the door without, place the food inside without looking and then leave. After a while as he opens the door he hears her crying out of lonlyness so he goes inside to talk to her to comfort her because he feels so bad for her being "imprisoned" in that room for so long. The story goes on like this for a couple more pages but I think you get the idea by now, eventually he get's her pregnant and kills her out of remorse all because of these "good intentions" that lead him to inapropriate situations.