How to word this?

I’ve been using my husband’s friend of 10 years for our bookkeeping and payroll (company to process our employee’s salaries). She’s the middle man between us and the payroll company and she’s been great. I recently looked up the payroll company she uses for us and the reviews aren’t good. Another big, reputable company has been wanting our business and the sent me unbeatable rates and they are one of the biggest payroll companies. Because we added an additional person to payroll recently, we also need worker’s comp. The big reputable payroll company also has workers comp so it would be easy to just have them handle everything. I rather they handle everything (worker comp and payroll). I feel really bad leaving our friend and moving payroll to someone else. She’ll remain our bookkeeper but the move is good for the company. I do feel very loyal to her, though, so it’s hard and she does take things a little personally. How would you word it so the blow isn’t harsh?