Mother In Law - religious issues

So basically I got married about a year and a half ago. My husband and I were both brought up in different religions but neither of us believe in God so when we got married we got married via a Humanist wedding (a totally legally binding wedding)

My parents were more than happy with our decision and paid the majority of the wedding for us and his parents were okay with our decision too (or so I thought)

We had a beautiful ceremony and an incredible day altogether. Many people commented that it was one of the best weddings they had been to.

About a month after our wedding I was out on a night out with my MIL and SIL and we all had loads to drink. On the way home my MIL pulls me aside and states that although she had a wonderful day it didn’t feel like a “real wedding” because it wasn’t done via the Catholic Church. Now I HATE confrontation so I told her that I offered to my OH to get married in a chapel if that’s what he really wanted (which is true and he declined because he doesn’t believe in it) but basically she’s telling me that we wasted our money in doing what we did because it wasn’t a “real wedding”

I mentioned it to my hubby who was raging and wanted to speak to her but I told him just to ignore it. I then find out that she made these comments to our guests on the day of the wedding along with being overheard in the toilet moaning “I never got to invite who I wanted” Now my parents and my hubby and I paid for our day. He has a huge family and they were all there. The people we didn’t invite that she wanted were people who didn’t even recognise my hubby and passed him on the street. Why should we pay for people that don’t know us and our seating was limited?! We couldn’t even get some of the people there that we wanted!

Anyway I’ll get to my point...I’m now pregnant and we haven’t announced it yet as it’s still early, only the important people know. I’ve just found out she’s told her friends and family when we told them not to which has annoyed me but I’m concerned that the whole religion thing is going to come up again.

We want to have a “naming ceremony” but I know for a fact that she won’t be happy as she already complains her other granddaughter isn’t christened.

Basically I feel like she wishes her son was married to a good Catholic girl rather than a Protestant (even although we don’t follow the religions we were brought up in!)

Am I being over sensitive? And how do I face this?