I really empathize with you and your situation...it must be extremely difficult to keep yourself calm when you feel like your options are limited, and you're in a country that doesn't offer the expertise you could find elsewhere.
That's a fairly high dose of omeprazole for a child, but I, of course, don't know anything about the history of what she's been through already. I would highly recommend trying another PPI. For example, it's possible that your daughter may get the same, or better relief, from a twice-daily dose of 20mg Nexium...or other PPI, for that matter. The effect of PPIs is cumulative over a few days, and they have a half-life of about 10-14 days. So, to be on 80mg per day is quite a bit, especially, I would think, for a child.
Also, without knowing her age, or size, perhaps there is some wisdom in waiting until she grows more before having the Nissen. It's possible that her growth over the past three years has impacted the Toupet. I also know that you want to keep to a minimum the "redos" to laparoscopic procedures. It's not an insignificant surgery.
How about diet, times of meals vs. bed, and other things to manage the reflux? These things will help, although, not eliminate symptoms. All this must be very stressful on her too, and that may increase acid production.
You know your daughter better than anyone else, and you're going to have to gauge her age, size and weight, severity of the condition, response from medication, and quality-of-life. If your daughter is old enough, include her in this decision as well.
Hopefully some other members will chime in...