A female that is grown will eat medium rats. At 450 grams, yours is far from being big enough for mediums.
If she'll take them, feed her one small rat/week. If she refuses the smalls, then offer her a weaned rat every 4 or 5 days until she has put on some more weight and is comfortable with smalls. Around 500 grams is when they typically start taking smalls without hesitation. Mine stay on small rats until they reach the 1200 gram mark or so (then they go to mediums), but that very much so depends on the specific snake.
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