Well, on the basis that you are holding the property as Tenants in common, you do have the right (if you wanted) to go to Court to obtain an Order for Sale- ie force a sale even if your sister does not wish to.
As regards ***** ***** half share of the property, you can legally do this, but it is doubtful that you will be able to find a party who is willing to pay half the market value of the property for the half share.
I may be wrong, but I think you ar ebest to go back to your sister and say that you have taken legal advice and that unless she willingly consents to a Sale, you will have no alternative but to issue Court proceedings and obtain an Order for Sale, and that you will ask the Court to make her responsible for the costs! Hopefully, the mere threat of this will make her see sense.
Of course, the othe roption is that if she wishes to retian the house, she should consider buying you out of your half share, if indeed she could secure a Mortgage to finance this.
I hope this assists you and sets out the legal position.