What happens if you feed her hourly for the 3-4 hours before bed? It might buy you a longer stretch before the waking starts.
In a similar vein, the "no cry sleep solution" book has a list of foods that are high in tryptophan and hence promote sleepiness. Avocado, yoghurt and turkey are ones I remember - but it was a longish list.
Big hugs from me too!
Was just thinking - 90 minutes is a typical sleep cycle (ie. most people wake up every 90 minutes and then go back to sleep without effort). If Seven is waking up 90-minutely that suggests that she can't go to sleep without your help. There's a couple of threads of people with this problem - i'll try and find them.
OMG... she put herself to sleep! Without one single tear!!!! is pretty close