She had a commanding, overbearing manner and could be petulant when balked.
According to Cadsuane Melaidhrin, she is the best Healer among living Aes Sedai and the best that the Tower has seen in centuries, perhaps ever. She has the ability to modulate perfectly the strength of the Healing weave accordingly to necessity (which very few people can do), meaning she can control the extent to which Healing will heal a person (and the amount of energy it will cost that person's body). This is very useful for dealing with life-threatening injuries, as shown when she Healed Dobraine (if she had used too strong a weave, he would have been killed by the shock). She has also the same ability with Healing as a full circle.
The only other people in the series with Healing ability possibly equalling or surpassing hers are Suana Dragand, Nynaeve al'Meara, Semirhage, the Asha'man Damer Flinn and Sumeko Karistovan of the Kin. Other Yellows such as Corele Hovian, Dagdara Finchey or Chesmal Emry are close, but Samitsu is still better.
As a Healer, Samitsu does not care if she gets bloodied or messy.
She is with Cadsuane and Niande in the rebels' camp just outside Cairhien when they are attacked by Padan Fain with Mashadar (or a bubble of evil is hitting the camp and Fain is using it in his favour).
She manages to stabilize Rand al'Thor after he is stabbed by Padan Fain with the Shadar Logoth dagger. Subsequently, after witnessing Damer Flinn's Healing on Rand's wound, she offered him gold, and even to bear his child in exchange for an explanation on how his Healing was accomplished. Her confidence in healing was somewhat shaken after witnessing Damer Flinn's healing, though it was restored when Cadsuane reassured her that she was the best Healer.
She is left in charge by Cadsuane in Cairhien after she leaves for Far Madding, searching for Rand. Unfortunately Sashalle Anderly doesn't submit to Samitsu authority due to her standing far higher in the One Power and has begun to take command.
Samitsu feels her control slipping away as Sashalle asserts herself while Loial and Karldin arrive in the Sun Palace and then Rosara announces Logain and many Asha'man and and Aes Sedai are entering in Cairhien.
Cadsuane sends her back to Cairhien, to keep an eye out for every activity of Sorilea, Sashalle and the other sisters there carry out. Cadsuane also thinks that Samitsu is a very good and capable Aes Sedai, but sometimes she needs to be reassured about her capacities.
Rand trusts Corele and Samitsu more than most Aes Sedai since they, along Damer Flinn, saved his life earlier.
When Dobraine was sent by Rand to Arad Doman the two Aes Sedai Sashalle Anderly and Samitsu Tamagowa took unofficially the stewardship of Cairhien for a while, until the coming of Elayne as new queen.
It can be safely assumed that Samitsu, like the other Aes Sedai in Cairhien, participated in the Last Battle. During the fight as a Yellow she probably stayed at Mayene to provide Healing to the injured. It is presumed that she survived the conflict.