Bridesmaidsssss!!!

As PP mentioned, you have plenty of time to see how your relationship develops before you need to make a decision. I personally think that asking someone to be in your wedding party just to have even sides is an awful idea and sure to set you up for drama.

I second this. I would suggest re-thinking your equal numbers. We have uneven numbers (my side) and while it might look a little funny, I'd rather us only have people we genuinely want stand with us instead of adding just for the aesthetic of it.

You still have a little over a year before the big day, so take a few months and get to know your co-worker a little better. Meet up at a local pub for weekly trivia nights, or a Saturday walk in the park with your dogs, double date with FH, etc. Make sure you still gel outside of the workplace and get the friendship on the next level

If you already feel certain the friendship is at that level, then I would definitely still make a point to ask her in person and outside of work...Maybe take her to a happy hour or any of the other activities mentioned above! Also make sure you give her time to respond, and no pressure to answer immediately mid-appetizer! Good Luck

If you haven't ever hung out outside of work, I wouldn't ask her. I'd have uneven parties like most weddings do now. If you really need even sides for some reason, I'd try to form a friendship outside of work before asking her.