Every person is different. I have a friend who took her mom with her and got zero reaction except for, You look nice.
On the wedding day though, the mom freaked and was like, you look so beautiful!
When I went for my dress fitting and found The One, the dress that I just felt like a princess in, I came out of the fitting room and my mom's entire face lit up! She was more excited than me and kept making everyone in the store come look at me in the dress. LOL. She was so funny about it.
I wouldn't read too much into it. It's your wedding and you need to pick out the dress that makes you feel like a rockstar!