Here is the the amazing Raina Kabaivanska (another link here) in 1977, singing "Io son lumila ancella" from Adriana Lecouvreur at Verona:
And again in 2009, at age 74, for a benefit:
Tosca, 1980, La Scala:
I would encourage you to look at as many clips as you can find. A true artist, a great singing actress.