Load Index Rating question

Hey everyone I am in the market for 2 new tires for my wife's car, she purchased 2 with a 93 load index rating and I was wondering if it would be ok to get 2 more with a higher rating such as 94 or 95 for the rear of the car. Will this cause any driving problems? also what about speed rating can these be mismatch as well? not buy much maybe W and V, thanks in advance for your help.

Avoid mixing mis matched tires if at all possible due to handling and stability problems.