Sounds to me like your only relationship with the person is online. If that is the case, I would drop it. I could preach free will and its wrong etc. Instead I will tell you from experience. Unless you live with someone for years, moment by moment, or have an extremely open relationship, you do not fully know them (unless your a mindreader rofl). I did a love spell as a kid, and suffered greatly for the results. Turns out the kid I grew up with (we were teens) was not as wonderful as he seems. If you still want to do it and have no worries, there are tons of spells out there, and you could make your own as well.
Love, light and Blessings :)