well he wont be happy go lucky or anything but DUTY AND HONOUR means he wouldn't ignore a person, and he'll always answer questions! Especially for Waver's friend, Waver is Important Friend so friends of Waver are Also Important by proxy! So if she locked called him he'd answer and handle her with his general graceful ease

But yeah, you can assume he taught her how to get it activated I guess? Basic activation will exhaust you quickly but give you a str/sta/agi type boost for a short period. How far he got teaching her to swing a weapon is up to you, Lancelot is like The World's Most Patient Man Ever so he'd easily wait out her bluster but she obvs isn't physically the strongest so take what you desire from him strategy wise.