Is this too formal for a wedding reception?

I bought this dress to wear to a friend’s wedding. I removed the decorative pin on that front sash, because I thought THAT was too much. But my mother has planted the seed of doubt in my head that this dress is too much for a wedding reception.
The wedding itself (which I won’t be going to) is an afternoon, garden wedding. The reception is in the evening, adults only, open bar, it’s a nice venue. I got a black sweater to go over this dress – and I was going to wear black shoes & a black purse. Is this too formal? Is my mom right?