No, in YS there's a character literally called Mary Sue. That's her front and center, and she's a little tween edgelord.
Considering Mary Sue name is better known as a self-insert/overpowered character trope (the male variant is called Marty Stu/Gary Stu), I think it's better to give this character a qualifier.
I'm pretty sure front and center that's Tanya, well into the future. My (vague) recollection is that in the Web Novel (which is now non-canon, some parts repeat but the LN does diverge too) after the war Tanya joins notAmerica for the notManhattanProject against the commies, aging and changing her hair color. She never broke the rules, and as an extremely valuable secret asset her existence and role in the war gets covered up by all sides. Similar in some ways I guess to german scientists who joined the US rocketry effort post WW2. Her eyes turn gold when she utilizes the Type 95. Mary Sue is dead, put down by her own side IIRC after repeated insubordination, loss of control/interest in revenge, falling for obvious commie plots, and general craziness. Militaries don't need loose cannons no matter how powerful once an immediate crisis passes.
Front and center is Mary Sioux, not Tanya. Tanya is at the top, holding the pistol.
On the left are the foreign (Legadonian?) volunteers sent to Union: Vivi at the top, COL Drake at the bottom, and I don't know the name of the third Volunteer in the middle.
On the right above Visha are two Republic soldiers. I don't know their names or ranks, but the one with the moustache is the commander of the troops in the Southern Continent.
At the top in the background are Anton Sioux and Lorya, flanking Tanya's arm.
Thats something a few people in the Navy with me who watched the anime/read the manga/LN had trouble accepting. Tanya didnt commit any war crimes throughout her entire career so far as I have seen. Every one of her actions has been acceptable under the laws of modern warfare, evwn if she was pushing them to the very limit of what the black and white said. Nothing she did is illegal under international law. Not even turning that city into a confligration was illegal because the remaining people of the city had declared themselves as combatants and killed the none combatants in front of them.
