Angel isn't such a good fighter then Buffy remembered. Or it's just because she grew up, learned - Angel didn't.

Author's Response: I think he might be out of practice seeing how he spends his time in a law firm plus Buffy remembers what he was like when she was 18 which is the last time she really fought by his side. I think they just grew in two different directions. She learned a lot from Giles and Spike as well and he didn't.