Oh yes, we are definitely bringing a copy of our marriage certificate. Forgot to mention that in the OP. We live in CA and as far as I can tell, there's no law against retaining your old ID. The license number stayed exactly the same between her old and new ID. The main issue, as mentioned below, is that TSA no longer just compares the ID to your boarding pass. The ID has to be inserted into the reader and compares it to existing passenger lists, so her new ID won't match.
According to this post from the TSA, you can travel with an expired ID up to 12 months past expiration as well.
The issue here is that the old license isn't simply expired. It is an invalid ID now that name has been changed. (Most states don't care about a simply expired ID, an ID that is now invalid due to name change is a different issue) You're correct her new ID won't match. This is why you need the marriage certificate. This is what will document to TSA that the person named on the ID is in fact the same person named on the BP.
Over-zealous TSA agents are our primary concern. I'm sure DL will figure it out, especially if I call and have them make a note on the PNR. Fortunately, we are not dealing with international borders on this trip. Her new passport hasn't arrived yet anyway. I'm guessing she won't be able to use her Pre-check since she changed the name on that already. I think we'll just show up earlier than usual and be prepared to spend some time with TSA.
Exactly. RNO just started doing the ID scan in the past couple of months, otherwise I would probably just buy a refundable fare for her on WN or something like that.