The solution to this situation is to call the blood bank, ask them to fax or tube over a policy on what is compatible with blood, and then, smiling sweetly, hand it over to this nurse.
Your unit should also have a blood policy in the unit manual so you could copy this and give it to her to read. Her thinking is incorrect, as far as I've been taught, and she could potentially harm a patient this way.
The AABB says:
"No medications or solutions may be routinely added to or infused through the same tubing with blood or components except 0.9% Sodium Chloride, Injection (USP). Other solutions intended for intravenous use may be used in an administration set or added to blood or components under either of the following conditions: a) They have been approved for this use by the FDA or b) There is documentation available to show that addition to the component involved is safe and efficacious. ABO-compatible plasma, 5% Albumin, or Plasma Protein Fraction, or other suitable plasma expanders may be used with approval of the patient's physician."
is the site; they have a Blood Administration sheet that your blood bank should have on hand.
Also found this online:
Lactated Ringer's or other electrolyte solutions containing calcium must never be given with blood or components which have an anticoagulant containing citrate. Small clots may form in red blood cell transfusions mixed with calcium containing solutions. Five percent dextrose in water or hypotonic sodium solutions can be also be hazardous if mixed with red blood cell units as they may cause the red cells to hemolyze. Other fluids must not be given through the same line with blood unless there is sufficient data to ensure compatibility. If plasma needs to be given at the same time as red blood cells, whole blood should be considered to decrease donor exposure.
This is a case of "Prove it" IMO. Check out the pamphlet from the KCl and investigate.