The LIb Dems may vote with the Tories if it the Tories are proposing something which is essentially a LibDem policy, such as making better provision for dealing with mental health. Norman Lamb has strongly argued the case for this for many years.
This is not the same thing as voting with the Tories to keep them in office. It is more akin to the Tories supporting Stella Creasy's QS amendment to allow women from NI to have free abortions on the mainland. No-one has suggested they did that to help the Labour Party.
The LibDems will continue to oppose most Tory policies, as they did when they voted against invoking Article 50, unlike Corbyn who instructed his MPs to support the Tories, imposing an unnecessary three line whip which fortunately many ignored.
The LibDems will not enter any coalition or DUP-type deal with May's government.