Mum,
This may be a shock to you. My girlfriend turns 50 this year. I know she is just a few years younger than you but I love her so much. I know that you think she is 35. We didn’t dare tell you the truth from the beginning due to your heart condition. So, we want you to come to the big birthday party that we’re throwing this August. You don’t have to bring a present, just be there and be happy with us.
I love you very much and I hope you are not mad at me for not telling you the truth from the start.
Angelo