So after one month of mana breathing suddenly she can kick ass too? Honestly I'm just more annoyed at the title than anything right now. 3 chapters in she becomes skinny and pretty from mana breathing, next chapter every servant changed opinions on her, she's smart, can talk snappy (which shocks everyone because the original character isn't like that), loses weight and is beautiful, and now she can fight... Yeah this really seems like mary sue material, she's really overpowered imo. She claims in her thoughts to have been training all the time, but we see none of that so it's all just random plot device for her to look good and save a potential love interest.
Some stuff is ok, but all those characteristics with very little time for development doesn't give me room to care all that much for the characters or the MC. The plot is moving way too fast for me and there's all these things that she could suddenly do. Next thing we know, there's going to be an accounting issue or something and she'll know the answers, or something.
The author really should've named this something else because there is no "Ugly Lady" anymore. If anyone wants a good isekai story with a chubby MC who works hard to lose her weight and use her intelligence, I highly recommend "I'll save this damn family."