She was a niece of the Emperor Trajan.

From Wikipedia:

Salonina Matidia (4 July 68 – 23 December 119) was the daughter and only child of Ulpia Marciana and wealthy praetor Gaius Salonius Matidius Patruinus. Her maternal uncle was the Roman Emperor Trajan. Trajan had no children and treated her like his daughter. Her father died in 78 and Matidia went with her mother to live with Trajan and his wife, Pompeia Plotina.

Between 81 and 82, Matidia married a suffect consul and former proconsul Lucius Vibius Sabinus. Sabinus died in 83 or 84. Matidia bore Sabinus a daughter called Vibia Sabina, who would marry the future Roman Emperor Hadrian. Matidia was very fond of her second cousin Hadrian and allowed him to marry Vibia Sabina.

In 84, Matidia married for a second time to an otherwise unattested Roman aristocrat called Lucius Mindius. Matidia bore Mindius a daughter called Mindia Matidia, commonly known as Matidia Minor. Mindius died in 85.

It is possible that Matidia also married a suffect consul of 88, Lucius Scribonius Libo Rupilius Frugi Bonus. Frugi had a daughter called Rupilia Faustina.[1] Faustina would go on to marry the Roman senator Marcus Annius Verus, to whom she bore one daughter and two sons. Through her children, she would become the grandmother of the Roman emperor Marcus Aurelius and his wife Faustina the Younger.

Matidia often traveled with her uncle and assisted him with decision-making. Like her mother, Matidia was honored with monuments and inscriptions in her name throughout the Roman Empire. On August 29, 112, she received the title of Augusta.

When Trajan died in 117, Matidia and Plotina brought the emperor's ashes back to Rome.[2] In 119 Matidia died, whereupon the Roman Emperor Hadrian delivered her funeral oration, deified her and granted her a temple and altar in Rome itself.[3]

References

1. Matidia the Elder, from Livius.org.
2. William Smith. "Matidia". A dictionary of Greek and Roman biography and mythology. London. John Murray.
3. Samuel Ball Platner (as completed and revised by Thomas Ashby). A Topographical Dictionary of Ancient Rome, London: Oxford University Press, 1929. "Ara Matidiae" & "Templum Matidiae". Retrieved from LacusCurtius on 20 December 2008.

   ---

   
   

http://circlevirtuous.com/fam559.html

Salonia Matidia

Salonia Matidia (4 July 68-23 December 119) was the daughter and only child of Ulpia Marciana and wealthy praetor Gaius Salonius Matidius Patruinus. Her maternal uncle was the Roman emperor Trajan. Trajan had no children and treated her like his daughter. Her father died in 78 CE and Matidia went with her mother to live with Trajan and his wife, Pompeia Plotina.

Between 81 and 82, Matidia married a suffect consul and former proconsul Lucius Vibius Sabinus. Sabinus died in 83 or 84. Matidia bore Sabinus a daughter called Vibia Sabina, who would marry the future Roman Emperor Hadrian. Matidia was very fond of her second cousin Hadrian and allowed him to marry Vibia Sabina.

In 84, Matidia married for a second time to an otherwise unattested Roman aristocrat called Lucius Mindius. Matidia bore Mindius a daughter called Mindia Matidia, commonly known as Matidia Minor. Mindius died in 85.

Matidia later married Lucius Scribonius Libo Rupilius Frugi Bonus, who was suffect consul in 88. Matidia bore Frugi a daughter called Rupilia Faustina. Faustina would go on to marry the Roman Senator Marcus Annius Verus, to whom she bore one daughter and two sons. Through her children, Faustina would become the grandmother of the Roman emperor Marcus Aurelius and his wife Faustina the Younger, as well as Marcus's sister Annia Cornificia Faustina.

Matidia often traveled with her uncle and assisted him with decision-making. Like her mother, Matidia was honored with monuments and inscriptions in her name throughout the Roman Empire. On August 29, 112, she received the title of Augusta.

When Trajan died in 117, Matidia and Plotina brought the emperor's ashes back to Rome. In 119 Matidia died, whereupon the Roman Emperor Hadrian delivered her funeral oration, deified her, and granted her a temple and altar in Rome itself. She thus became the first divinized Roman woman to be dedicated a full-scale temple of her own, as opposed to one shared with her husband or a smaller shrine.

Source :

https://en.wikipedia.org/wiki/Salonia_Matidia