That's a pretty heavy infestation. I wouldn't recommend using neem any more that far into flower. Once again I'll push this product -
https://www.amazon.com/Bio-Pesticide-All-Natural-Insecticide-Pesticide-Better-Insects-Non-Phytotoxic/dp/B07PH46H8K/ref=sr_1_2?crid=3MGK255QZ9BKG&keywords=agromagen+growsafe&qid=1694994622&sprefix=agromagen+growsafe,aps,183&sr=8-2
Agromagen Growsafe Biopesticide. 100% organic/OMRI certified, won't burn your plants like neem, won't leave nasty smell/residue like neem (does have a slight "deep fryer" smell when you initially spray it, but this goes away after a day or two)
Works so well that I've been recommending it to everyone. One spray will eliminate 99% of your infestation, 2 sprays will eliminate 100% and 3 sprays will definitely make sure they never come back (for the season)
It's a little pricey but it works extremely well and imo worth every penny! Even kills eggs. Safe to use from clone through harvest.
Make sure you spray the entire plant very well, taking special care to spray UNDER the leaves very well, as this is where spider mites lay their eggs and spend most of their lives!
Also, this stuff works great for prevention of mold in your buds!