Coolant bubbling in overflow reservoir

Recently my coolant in my overflow reservoir has been bubbling and dripping out of the top overflow hose. It’s been hot lately and has only been happening when the A/C is turned on. Even if it’s only on low. Without A/C she is totally fine but this is definitely a new problem. I have done an oil change and flushed my coolant there is no mixture of the two together. Already checked for leaks as well. She doesn’t overheat either, she stays at her normal operating temperature. I already know that it could be a head gasket problem but I want to make sure that I know of any other possible problems it could be.