TAS Tree neighbour issue

Neighbour has 2 trees at edge of property next to ours. One tree dead, one shedding branches onto our land and almost dead. Each is 30-40 metres high. Five weeks of asking neighbour to remove trees due to safety issues and that we wish to build on our property but trees posing danger so cannot start building.
What do we do pls? Have asked her to give us written permission to remove trees at our cost.
Neighbour agrees then won't sign to give us permission. Sixth week coming up and were hoping we d have somewhere to live but looks like we LL have to sleep in a tent now until trees are down
Pls any advice!

P.s trees are Pinus radiata
They are deemed weeds by council

[we paid in the end.
It was the quickest way.

For reader info:
Council do not become involved in tree issues unless on council land.