How do you get someone to stop falling in love with you?

dont take any showers
The usual understanding of falling in love is that some one attaches, wants to see and be with you all the time. As real love is totally free and does not require your presence or any one else to manifest itself, that attraction is nothing but a normal human-animal behavior.
You can not avoid some one to be attracted to you, but knowing that that is not really love, now you can handle that person without fear, kindly and with real love (which is detached) until this person obsession with you goes away. Obviously, however you must not pursue any other contact than the strictly necessary so that your message of not interest can be clearly understood.
The fact that you realize and care about what is happening to the other person shows your compassion and tact.