@Jimmyhats it's pretty much like what
@tonie said. She was a teenaged orphan in her past life with no special features, and then she got abused until she was married off... I don't think the average teenager has a lot of time to learn about modern warfare or how to make advanced weaponry. She did the best that she could.
I do think it was a bit meh how she had to be saved by the ML instead of being able to fend off the attack on her own merits (like how she used her intellect to make the golems fight each other by exploiting their greed and stupidity in the previous chapters), but I also can't really think of any way she could've done so without it being OP or deus ex machina.