A: I assume there is no written agreement between you and your former partner regulating your co-ownership of the property in the form of a declaration of trust, a lease or even a partnership deed?
If so, you would have to fall back on your general rights as a property owner. You are certainly entitled to access to the premises (for the purposes of inspecting them and having a valuation undertaken) and to your share of the notional rent.
It would be wise to give at least 24 hours' notice of your intention to visit the premises (as this is the type of arrangement implicit under a lease if you had one).
If however your former partner is not co-operative, it is likely that you will have to take steps towards applying for a court order to enforce your rights. Putting your partner on notice that you will be doing so will urge her to behave more reasonably.
You will appreciate however that all this would have been made much simpler if you had had the appropriate documentation in place from the time you acquired your joint interest in the property - and certainly prior to the time of your retirement from the practice.