A 'lady-at-arms' is an oxymoron.
There are far surer and safer paths for a woman to achieve her aims than bearing arms. Most medieval ladies couldn't fight worth a damn. They weren't trained from youth like the men were, and no occupation penalizes the physical and mental disadvantages that women have as much as that of the soldier. I'd be planning on having a lot of dead ladies if I were you.
Also, MeestYk, I'd appreciate it if you didn't make stupid comments. If medieval men were gay you wouldn't be here shooting your mouth off.