As mentioned earlier, do you know how they are chlorinating this pool?
If its with stabilized products (trichlor, dichlor) those are highly acidic & tend to tank ph & ta.
The higher fc levels can bleach out the strips so there could very well be quite a bit of cya in the water even though the strip says otherwise.
With the water clarity/color issues you’re describing it sounds & looks like there is an algae problem.
The interim answer is add 5ppm worth of liquid chlorine to the pool each day to keep things from getting worse until they have a proper kit & can get accurate results to determine if there needs to be any adjustments before then doing the
SLAM Process to eradicate the algae problem.
Unfortunately that’s about all we can extrapolate from your current data.
Using liquid chlorine won’t adversely impact the ph or ta like other forms of chlorine. I feel they must be adding something or there wouldn’t be any fc left/it would be falling quickly if there truly is no cya & there is an algae problem.
I personally would decline swimming in this pool & cannot confidently say that it is safe to swim in with the info you have.
I would suggest pointing your friend to tfp and we can help guide them on getting their pool back in order. Although you obviously mean well, You are missing alot of important info so its very hard give accurate guidance.