Why will she simply not let you have a copy of the certified will?
Or can you obtain a copy from the solicitors that held it? Will help you when you obtain advice, as wording is all important.
Take it she has finished initial grieving if she has starting selling things. IMO (with no legal training) - just some life experience of having to contest a will / estate and exectors actions , your step mother should not be selling parts of the estate to pay bills. She should be paying her own way - hard but cruel though it seems, but if your father had forthought to make a will and she needs to adhere to his wishes.
As a note, after my experience, I changed my will so that no benefcers are excecutors. A bit more expense when I depart this world, but at least I know that my estate will be administered in a fair and businesslike way. For anyone following this route, you need to choose excectors wisely. Can be a minefield of hidden expenses.