6 years old girl suffering from severe constipation was given dulcolax suppository. she had a big bowel movement after that and now only passing very small amount of very liquid stools.she is on lactulose. does this mean her constipation is over?

Maybe/not: The lactulose will tend to keep stools very loose/watery. If a large stoop was blocking the exit & the suppository helped it out, the issue may be over. However, you may be better off slowly reducing the lactulose over several days/weeks. The most common reason for return of constipation at that age is ending treatment too soon. Common treatment time is 2X the duration of constipation.