|Working within the default kit she comes with, Caeda is a very capable counter-mage. The only mages she dies to are ones that can OHKO her. She's in a 5-way tie for most base speed of any unit in the game. (1st place is Lon'Qu, 2nd is Anna, and 3rd is both varieties of Caeda, Lyn, Setsuna, Felicia and Navarre.) What this means is the only units who can get double attacks on her must have +Spd IVs, and either Darting Blow or LND3, or are running B Tomebreaker.
If you have +Spd IV yourself, you don't even need to worry about LND3 mages (except other +Spd Bridal Caedas, I suppose). Nino and Linde, the next fastest mages, require the +Spd seal or Speed buffs to get to the magical 45 number. And you can always match that with your own team set up, if you find you need your Caeda to tank a hit from either of them.
If you manage to separate the green blade tome mages that are rampant in the meta from their Hone/Fortify/Rally support, you can even tank a shot from them. Fury 3 neutral Nino still requires +7 to her total damage to OHKO Bridal Caeda, while neutral attack Julia, Spring Camilla or Cecilia need +5. They are probably going to have the support to easily reach that threshold, but still. If you can separate them from the heard, you can tank a shot from them and if they aren't going to get a kill against some other unit in your party, they will gun for her because AI chases WTA matchups. Obviously, she fairs a lot better against other blue mages. Except Reinhardt. He still wins. Hopefully you have other ways to deal with him.
If you want to get silly with the anti-mage potential, you could feed her Blárowl for spur shenanigans. It'll also help her lowish attack, and definitely solidify her crazy speed, if you have more than one unit directly next to you. (Worth noting that Mae herself is a pretty capable blue anti-mage already so feeding her tome to Bridal Caeda is a bit redundant when you could just actually use her.)
When not fighting other mages, Caeda is as servicable a mage as you could expect. Her attack power may be a little on the low side, but that's fine because she's going to double pretty much the entire cast save a very select few units. When Iceberg procs, pretty much anything is dies. And she's buffing the defense and resistance of the rest of your team every time she lands an attack, which is pretty handy. She already comes with Hone Speed 3 default so that covers all the defensive buffs.
Reposition is fairly standard. Swap could work. Might even want to do Ardent Sacrifice depending on the rest of your team's needs.