I'm not 100% on sophie being an enitrely defensive character, but from my experience thats what vs Asta is about. Astas outside pokes are little threat to you if you're blocking a lot (and can do standard things like block 1A on reaction). Trying to rush him down can be a problem because sophie's mix-ups arent amazing and much of her moves for pushing pressure don't operate as they normally do (asta A+G beats sophie B+K for example) where as giving Asta advantage often is a dangerous long term strategy. Asta's pokes do have more range, but each has their own issues (some high, some dont track step, some not terribly safe) and if you can force a wide whiff you can hurt him for it. This doesnt mean spam TAS B all day, use it judiciously! You do need to beat his poke game if hes using it though, because as I said rushing him down is likely a bad idea. If you can convince him to come in on you then you need to push him away a lot. Stuff like B/BB, WS K can work as an example along with liberal application of backstep in conjunction with guard. Try to guess some run in's and attack them too he's got bullrush but he can't use it everytime. You have to play this fight pretty actively, but I dont think it's that bad.