I do not think Russia will launch a full scale invasion of Ukraine. Russia will recognise that the main population of Ukraine outside the eastern cities is very hostile to Russia, would offer strong resistance to invasion and refuse to accept attempted rule. Crimea has accepted Russian rule as there was a much larger pro Russia population in that part of the country when Russia marched in without resistance.
Russia pretends to believe that NATO is a threat to it, yet there is no evidence that NATO has ever wanted to expand its territory by military means. All NATO troops and weapons deployed in the eastern member states are there for defence only. NATO makes no territorial claims. It is true after the split up of the USSR some states asked to join NATO. They were not made to by an alliance often reluctant to accept new members given the burden they bring to the collective defence.
Russia will doubtless wish to foment tensions in Donbas further where there are more pro Russian citizens unhappy with Kiev rule. France and Germany tried to negotiate a peace in eastern Ukraine with Russia and the Kiev government. The Minsk Agreements sought a solution of devolved government for Donbas but the elections did not take place and we still await a constitutional settlement. It is best for that group to try again to adjust the Minsk Agreements to current conditions and get on with the implementation.
I am not surprised the Foreign Secretary got nowhere with the Russian Foreign Minister. I hope she now returns to end the talks with the EU and get on with putting in a solution to the Irish Protocol issue.