str_cpy can copy either STRING* to STRING* or char* to STRING*, so you should be fine there.

This however:
(txt_eventlog.pstring)[i] = (txt_eventlog.pstring)[i+1];
should be done with str_cpy()...

Maybe it also works your way, but I'm not sure whether it is good to bend around the pointers of a TEXT* object...
Also by default when giving a 'strings' number during definition of the TEXT* the strings will already be created, so you don't need str_create. This will just leave garbage in the memory.... if I understood the internals of a TEXT* object correctly...

jcl can answer this better than me I guess...