The mothers suggestion the baby was 'laughing along to the show' is so ridiculous I stopped paying attention to anything else she had to say after that
Time to put your big girl pants on Mum and consider waiting until you are comfortable leaving your baby for a few hours to attend a show where it may not be appropriate to take a potentially noisy 7 month old. I remember missing out on shows and events I would have liked to attend because it wasn't feasible for me to leave my child or to take them. It's a part of parenting and a part of life. It only lasts a short while and there are plenty more shows and plenty more ocacsions for you to attend when the time is right again.