The point about separation/divorce is to separate your lives and finances. You don''t have to agree to your wife''s proposal, but you need to be aware that if no agreement is reached your wife can apply to court and a sheriff would determine how the matrimonial assets are shared. He (or she) has the authority to order a valuation if necessary and the sale or transfer of the property. The costs of court proceedings aren''t insignificant, so you could lose a lot more cash and the property would ultimately be sold if neither of you want it to be transferred to your name.
Fiona is right, the difference in the reduction may cost more than that in legal bills, should it go that way. If it is not much of a variation then I would suggest trying to reach a compromise. The only winners would be the solicitors at the end of the day!