When living in Madeira, you will (I hope) interact with local women, single or married. If men are often known by their family name (Mr. Machado, Correia, Pereira, Silva, etc), you should not address a woman by her family name only, it will sound really weird.
So, knowing that Mrs is translated to Sra. (abbreviation of Senhora), you should address Mrs. Ana Silva by “Sra. Ana” or “Sra. Ana Silva” and not by “Sra. Silva”. This is valid for single or married women.
To a more delicate or sumptuous treatment, you may also use “Sra. D. Ana Silva” (D. means Dona, an old treatment to distinguish more wealthy women in old days). This is a must if you are in mainland Portugal and it is also used in Madeira but it shouldn’t be a problem if you use only Senhora.
If you are a close friend to the woman you are addressing, if you know her well, or if you’re relation is really friendly, then you’ll just call her Ana.
Remember: Portuguese women are proud of their own name!