I need advice!

ok,

I’m invited to a wedding shower but not the wedding itself. I found out why! The classmate (Bride) doesn’t like me very much, but the groom does. Other classmate show me a group text.
Bride: I don’t know why I’m inviting her(me), she is so ugly and kind of chunky.
Bridesmaid #1: hey! That’s not nice, she’s friends with your fiancé.
Bridesmaid #2: Just invite her to the shower and be done with it.
Bride: ugh, fine, just make sure she stays out my way. Classmate didn’t show me more. Bride has 6 bridesmaids!

What do I do, Do I go or say something came up and decline?

What on earth? She's expecting you to come to the bridal shower (with a gift!) and not the wedding? That is so weird. I'd decline in a heartbeat.

She is rude and insensitive, not to mention tacky. You don't owe an excuse (actually ever!)...just send a polite "not able to attend". She doesn't deserve a moment of your time. 

@Wox and PaintItBlonde,

Thank you, I might decline, I’ll talk to the groom later, to let him know, I might be declining.
He doesn’t know about the group text and I don’t think it’s my place to tell him.

Well, that's an ugly little spot she's put you in, isn't it? I agree you shouldn't attend, and I think you are totally right in not bringing the texts to the groom's attention. He's your friend and you'd then be putting him a similar situation. Good Luck with your decision!

@Blackcat41-

Thank you, yeah, I known him since elementary. I’m sure, he’ll know eventually.
She (Bride) is not evil, she has a mean streak and is brutally honest.
She is just stressed from planning a Wedding, she’ll calm down when it’s over.

Kindly decline. How rude and tacky of her. 

It's weird you would be invited to the bridal shower(generally just the bride is here) and not the wedding when you are friends with the groom and not the bridge. 

I would tell the groom. Wedding stress is not a valid excuse to insult someone the groom is close with. The dude deserves to know who he's marrying. Divorce is nasty, expensive as heck, and a nightmare especially if they did not have any prenups and if they have children. I've seen enough horrors where families and friends knew about the bad side of the fiancee/fiance and didn't warn the bride/groom and it blindsided the bride/groom. It usually led to a miserable marriage and nasty divorce once the fiancee/fiance begins to reveal their true side after the marriage. Don't twist anything and share your opinions, just share the facts. Show him the text evidence and let him make his own decisions. If he chooses to marry her anyways, that's his choice but at least he has a choice.

Update: 

I called the groom and declined, he asked me why and I told him to ask that one bridesmaid for that group text.
I feel really bad now, I have never been a snitch and never will.
Am I evil for snitching? I know there will be consequences for my action! I probably still be friends with him, but I will forever lost my friendship with her (Bride).