I think she have this mental illness called crush fetish
A crush fetish is a paraphilia which primarily consists of the desire to see others (generally members of the opposite sex) crush small creatures such as insects, mammals and reptiles. Inanimate objects, such as cigarettes, fruit or toy cars, can also be crush fetish stimuli. The term "crush fetishist" also refers to those who perform the crushing.
This sexual fetish is popular amongst many foot fetishists[citation needed], as crushing by feet is usually the main focus (although other methods are implemented, such as sitting on the target object). The foot (barefoot or in shoes) is thus often idolised in crush erotica such as magazines, audio tapes and crush films.
Taken from wiki pedia: read more there
http://en.wikipedia.org/wiki/Crush_fetish#Crush_filmsTo trample generally means to crush underfoot. Stampeding animals often cause injury to people by trampling them. During the Middle Ages, horses were sometimes trained to trample opposing soldiers.
In the card game Magic: The Gathering, trample is a common ability given to creatures allowing the creature to deal the remainder of their damage to the opponent after blockers receive lethal damage.
Trampling may also have a sexual connotation, especially when in relation to BDSM. It involves the act of the dominant stepping on and walking all over the submissive. This can be done sensually and barefoot, or more to cause pain with high heels or boots or other shoes. The psychology behind it is that the submissive is "underfoot" the dominant, and is below him/her (literally and figuratively).
Taken from:
http://en.wikipedia.org/wiki/Tramplingmeaning crushing stuff will make someone genital arouse if he/she have this mental illness.. i dunno got cure or not lea