It's preferable not to add flocculants to tanks but it is generally safe for fish and other aquatic organisms including turtles. Having said that, big water changes and gravel cleaning is the safest way to clear a tank. You might also need to improve filtration or change the food you give her.
If you have trouble doing water changes, get a gravel cleaner with a long hose and run the hose out the door. Gravel clean the tank water onto the lawn or garden. Then have a few plastic containers full of water next to the tank and use a water pump/ power head to pump the new water into the tank. Or fill it with the hose.
You can make a gravel cleaner from a 1, 1.5 or 2 litre plastic drink bottle. Cut the bottom off the bottle and throw that bit away. Remove the lid and plastic ring around the top and throw those 2 bits away. Put a plastic hose on or in the top of the bottle and you have a home made gravel cleaner. Most garden hoses fit in a plastic drink bottle and work well.
I used black poly pipe (irrigation hose) to fill my tanks. I had a tap connector on one end and made a U shape at the other end using 90degree elbows and short lengths of pipe. The U shape was turned upside down and hung over the side of the tank and held the hose in place while it filled up.
The reason I use black irrigation hose to fill the tanks is because normal garden hoses have a chemical in them that is used to keep the hose soft and flexible. The chemical is toxic to all animals, birds and fish, and leaches into the water flowing through or sitting in the hose. The black poly pipe doesn't have this chemical. The warmer the weather or the water, the more of this chemical that leaches into the water. If you use a garden hose to fill an aquarium or fill up a pet's water bowl, you should run the tap for a couple of minutes to flush out any chemicals in the water that is in the hose, then use the clean water to fill a tank or water the animals.
If there are no fish or shrimp in the tank, you can fill it with tap water and add dechlorinator to the tank while it is filling. You can also do a complete water change if the water is really bad.