You fall in love with someone when you share life with them, spend time with them, touch them, smell them and so on and these situations might also not be enough.
On line you can assume to be in love with someone, but you are in love with the idea and the opinion you have about them. For example you know I'd love to learn and improve my English and I try to talk with native speakers and many ladies have told me they are in love with me (just because I'm Italian and they think I'm a fantastic person (that might be true), but it is just their opinion about me). Actually, I'm handsome and debonair, but it is not enough to fall in love with me (maybe it is enough in my case, but I'm not the rule, I'm the exception!
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