Well, it can develop in such way, she asks internet about her strange "fantasies" about her horse, people tell she must prepare her pussy for "main event" and give her a link, using it she finds shop offering horse dildos.
She orders it "accidentally", feeling herself very dirty, when it arrives Myriam has no courage to use it, but after having erotic dreams about tempting strong horse cocks she finally dares to shove it into her pussy.
After learning to orgasm from its size, Myriam has a dream where she's riding on Hammer, naked, happy and free. Waking up she sees that she fell asleep with horse dildo still in her stretched pussy.
Myriam decides she won't be able to sleep peacefully until she tries the REAL one.