The worst good luck ever.

+atk no hesitation needed. drop vantage on her and she can deal with both rein and lyn initiating on her the same turn and kill both. She actually doesnt need speed for what she is supposed to do (one hit horsies and survive them) you IV is actually not bad at all

+Atk if you want to use her original Tome

Hmm... Well if you are running a blade then go with the -Attack because it doesn't matter as much with blade and even with -Attack her attack is comparable to Tharja and Nino so it's not terrible. However if you are keeping Keen Gronnwolf then it may be better to take +Attack and use something like Deathblow because the bonus damage is based on her attack and there's always the chance that even with +Speed she could miss the double attack and not kill (On units such as B!Lyn or Siegbert, for example). I do not have Rhajat, nor have I ever played around with wolf tomes so I'm not the most reliable source but I hope I help in some way.

+Atk for her weapon, +spd for blade tome