I will send an SMS to my dh if I need to remind him Of something or to pick something up..
If he is out I expect an SMS letting me know when he is going to be home and an SMS when he leaves to come home (he doesn't drive and uses public transport) just so I know when to expect him home and if he is late then I start to worry.. I also do the same when I am out.
While I like getting random SMS's from dh there is no way I could handle what you have explained your friend doing. I will send dh random SMSs to dh when he is out saying I loved him etc and I feel bad for that. I have trust issues but your friend is way over the top and needs to cut it out before he leaves her.