。
Even just fighting alongside me for a short while is more than I could ask for.
Literal
A-little [attributive-の] time [only-だけ][even-でも] together fight-[benefactive-てくれる] [only-だけ] [with-で] honorable-character is-[feminine-よ].
御の字 is a fixed idiom meaning 'more than enough, the best one could hope for, a godsend' — literally 'the honorable (御) letter (字).' The origin is obscure but the idiom is common in expressions of gratitude. ~てくれる adds the benefactive 'for me' direction, emphasizing that the listener's action is a kindness. The three ~だけ clauses build up a structure: 少しの間だけ (short time) + でも (even) + 戦ってくれるだけ (just fighting) + で御の字 (is the best).