That makes her the least experienced.I'm not saying,that she's weak,but she's definitely not as powerful as Francesca,Ida,Philippa,Sile and Yennefer.I'd say she's on the same level of power as Sabrina and Keira.
Except Sabrina is as old as Yennefer, and together with Keira destroyed a freaking castle.
To me, in terms of powers, The Lodge of Sorceresses' ranking lists:
1. Philippa (Tissaia's, the Archmistress of Magic, claimed she was her best student, Geralt regarded her equal to Vilgefortz, veteran of Battle of Sodden Hill and 300+ years old experiences never hurt)
2. Francesca (I'd say she's near equal to Phil, but we never see her in action, but she's well versed in supreme elven magics unlike human mages)
3. Sheale de Tancerville (more of a researcher type of mage, but she mentions she was asked to join both the Chapter and Council of Sorcerers, meaning she must be regarded as pretty powerful)
4. Ida (compared to the others, we know virtually nothing about her, except she's a Sage, which means she's more powerful than your typical human sorcerer)
5. Sabrina Glevissig (feisty woman, Philippa's second-in-command during Thanedd Coup, also fought at Sodden)
6. Margarita Laux-Antille (more interested in being a scholar, but being given such prestigious position must at least means she's skilled in theory. If Yennefer officially joined, I'd rank her as high as Rita)
7. Fringilla Vigo (she's not extraordinary skilled by any means, but she survived at Sodden and her mastery of illusion proved to be a blessing to Geralt in the very end)
8. Triss Merigold (a little below average, of course she got stronger in the games, as she's usually our go-to-mage companion, and as one of two LI to Geralt, she couldn't be that scared little girl she was at the Sodden Hill)
9. Keira Metz (she got K0'd pretty quickly at Thanedd, though together with Sabrina leveled a huge castle)
10. Assire var Anahid (ranked below her colleague, as her main interest lied in research and more scientific side of magic then in casting attacking spells, healing prowess, or anything that could be helpful in actual fight)
Of course, Ciri in her prime can beat any of them.