How to deal with important but lazy collaborators?
Honestly, this is a fairly common problem.  You see it  a lot at even the basic office group level where one person ends up doing a majority of the work.  If you've put in a lot of work and this is the only way forward then accept it and move on.  If you can't live with that outcome then pull your contribution and move on.  

In the future...well now you know what you look out for!

Either way, don't let this consume you.  There will be many more battles to fight in your academic career.