Issue with management

[MDelainy, ASN, RN]

Hi all,
I work at an infusion center as their full time nurse. We have another nurse who used to be there full time but her shifts are now divided based on patient load. I called out recently because I have a sore throat that has left me practically unable to speak and have been taking Motrin 800mg to help with the pain/inflammation etc. I was the only nurse scheduled for today and since there were no nurses to cover my shift, my manager had to go into work today. I usually do not call out unless I absolutely cannot go into work & request time off well in advance. My manager recently advised our office manager that she is feeling taken advantage of which caught me off guard and she also is scheduling a meeting for this Friday to air our grievances. No one person can be relied on 24/7 and it is not my fault that there is almost never enough coverage and whenever there is an emergency everyone is left scrambling bc upper management chooses to only have one FT nurse at each site and the rest per diem. Any advice on how to proceed?