Confronting Elin's years of training to that of other Aes Sedai it can be guessed that her level of strength is between the levels 38(26) and 45(33).
Elin is 47 years old. She was born in the year 953 NE in Andor and she went to the White Tower in 971 NE. After spending fifteen years as novice and fourteen as Accepted she was raised to the shawl in the year 1000 NE.
Elin was a novice of twenty-five when Gitara Moroso had her Foretelling about the Dragon being reborn. During that event Elin was in the anteroom of the Amyrlin's apartment, so she was not able to hear the words pronounced by Gitara. At that time she had been a novice for seven years while Moiraine and Siuan Sanche were able to gain the shawl after only three years as novices and three as Accepted.
Elayne Trakand mentions that Elin was the oldest Accepted when she arrived in the White Tower. Nynaeve al'Meara thought that they are the same age, but some time after she discovered that Elin's younger sister is about forty when she came to the Tower to visit her. So Elayne and Nynaeve guessed that Elin had been in the Tower for a very long time since she started as a novice. She has slowed in her ageing, because of using the One Power for so long, but still she has not gained the ageless look of an Aes Sedai. The case of Elin confronted also to that of Aiel Wise Ones and the Kinswomen permitted the two of them to guess that the Oath Rod is the cause of the ageless look and not a prolonged use of the Power.
Sometime during the course of the series, Elin took and passed the test for Aes Sedai and she is now an Aes Sedai of the Brown Ajah; so in total she spent twenty nine years as novice and Accepted, when a medium time for an average Aes Sedai preparation is around fifteen years. So many years learning the weaves indicates that probably Elin is not very strong in saidar, maybe around the level of Daigian Moseneillin, who stands on the lowest level allowed to become Aes Sedai, spending a longer time as novice and Accepted than anyone in memory.
Elin has remained loyal to the White Tower during the split.