The answer to your question really depends on the language in the option to buy. The option to buy may prevent her from placing the property on the market or selling it during the option period. If the option has been exercised, then that is also another story. You should have an attorney review the option to buy document.
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Your respective rights are determined by your contract, which I presume is in writing. Based on your question, it appears that you have more issues than just the landlord's plan to sell the property. You should contact a real estate or landlord/tenant attorney to discuss you situation sooner rather than later. Make sure to provide the lawyer with a copy of your lease and information regarding the landlord's attempt to sell the property.
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As advised, look to the terms of your option to buy contract. Do you have a right of first refusal? That terminology on the contract may give you the option to exercise the option you have or to match any offer from another potential buyer.