She should quit Labour and set up a new Blairite coalition. At the end of the day, an SDP-like situation of 1983 is absolutely bound to happen in this parliament anyway, considering Corbyn is winning. Or Tristram Hunt's coup of Corbyn will succeed. One or the other.
Whatever happens, if she wants to win, she needs to quit. There needs to be a successor party of Labour that is further to the right than Corbyn and further to the left than Lib Dems. That's the only place that they can realistically win, and in the words of Tony Blair yesterday "get a transplant if you believe otherwise"