The point is that she'll be able to actually do SOMETHING and not feel like an absolutely useless DEAD WEIGHT on the team. Look, I respect your view on this, but at this point, its just making you completely miss the very obvious point, lol.
If she came back in her original body, she'll just end up in the exact same situation down the line when they confront Freid and his lackeys. They're strong, as they also have ancient magic. A regular human wouldn't be able to do jackshit. The idea of staying in your original body just because it's your original body, only to be useless and fucking die again, causing potential team wipes/bad guys escaping vs going into an unbelievably stronger body while your original body has its time completely frozen to be kept for returning into...its pretty damn obvious what the choice would be if any isekai'd character had to pick.
I for one, would gladly move my soul to another body if it meant it was a direct upgrade from the current me in every aspect. Not like theres anything special about the current me. Though, I understand others wouldn't want that, since there already exists that one condition where people don't feel like their body is theirs or something, Idk, not a medical person, lol. Someone probably knows what I'm talking about.