Soft resetting for shiny Mudkip in gen 3 and I currently have a 3 female combo, the max I've had so far was 5.

Pure curiosity here :P

Bonus: how many female mudkips would I need in a row in order for it to equal the same odds of a Gen 3 shiny?

To calculate this, it's just 12.5%^5, which is 0.003051757%. This is actually rarer than a shiny Pokemon, which is 0.012207031% in Gen 3. Getting four female starters in a row would be closer to the rarity of a shiny Pokemon, with a 0.024414062% chance to happen.