Technically once she has signed the contract, she is bound into purchasing the apartment.
However, afaik her best bet would be contact the selling agent and explain her prediciment to them. IF they have a prospective purchaser for the apartment for example on a cancellation list - it could be possible to transfer the purchase agreement. I say could, not would. Otherwise she could be left in a position where she continues with the purchase and sells the apartment as is.
If the apartment has significantly appreciated in value over the past 18 months then possibly she could do this, and not be at a loss as regards legal fees etc.
HTH