I can see her point but it really drives to the difference between the nature of sacred liturgy versus Protestant services. I would take a more positive approach rather than criticizing her way of worship.
Some thoughts come to mind. First, while the mass may seem monotonous to her, for those of us who understand the nature of our liturgy we find it both moving and beautiful. It is anything but boring. Imagine someone pointing out that when she is deep in prayer to Christ that she doesn’t look like she is having much fun. I think she would agree that there is a time and place for fun and contemplative conversation with Christ, or for us the sacred liturgy is probably not the place.
Second, she needs to understand that we believe that the consecration brings Christ to us body, soul and divinity. I would ask her if the nature of their services would change if Christ were truly present on the altar. I think in all honesty it would. And point out to her that just because she doesn’t believe doesn’t mean He isn’t there.
Third, for those of us who make a habit of attending mass when traveling, on vacation, and otherwise away from home, we find great comfort in the consistency of the liturgy. Think about the fact that on any given Sunday hundreds of millions of people (possibly more than a billion) are having the same Mass in their vernacular with the same readings, Gospel, etc. I have noticed that many of my devout Protestant friends don’t attend services when they are away from home because it isn’t their church. It is of the many beautiful aspects of our faith.
Finally, rather than criticizing the fun they have at their service point out that Catholics are a pretty fun loving group of people. Having said that, there are any number of parishes that have evangelical groups that are pretty lively.