As seen posted photo the horizontal line and gummy smile might improve with a BOTOX injection. Or even a surgical release of the muscles in the upper lip...
To completely give a good option as to what may be done to assist you a physical exam is an absolute necessity. It appears that you may either have an overdeveloped perioral muscle or the skin overlying the perioral muscle is scarred down to the muscle itself. The treatment for either situation is very different. Botox may be used for the overdeveloped muscle but surgical release is required for the attached skin. Filler would do little good for either situation.
The line above your lip is likely caused by
movement and although it may soften a little with filler it will not go
away completely. At times, Botox can be used, if being administered by an
experienced injector to try and modify the movement to diminish the appearance
of this line. You must be aware that you may not like the end result as the
upper lip may drop slightly and the overall shape of your smile will change. My
best is advice is to take baby steps and try the filler first. If you are not
happy with that or the filler doesn’t last very long, due to movement, you can
always add a little Botox the next time.
I do agree that it is possible Botox in the upper lip muscle would help soften the crease, and additionally reduce the prominence of your gums when you smile. I would like to see a picture of your upper lip at rest to see what it looks like since the filler.
It look like you have over active muscle in the upper lip and perhaps botox may help soften that line by diminishing the activity, but an exam in person is critical.