Hi !!
David- Mme Beaufour , est-ce que vous vous êtes blessée ?
(passé composé de "se blesser". Pronominal verb . Past participle feminine singular ---> agrees with vous = Madame Beaufour)
the "vous" is a "vous de politesse", so it remains singular as it is for one person only , Mme Beaufour
Mme Beaufour. Oui, je me suis blessé la jambe. (I injured my leg myself)
(passé composé . Past participle is invariable because the object complement is "la jambe" . You could say = j'ai blessé ma jambe. So you have to take the rules of the passé composé with avoir. Here it's not anymore the pronominal verb "se blesser" but the simple verb "blesser"......
David- Luc, ta mère s'est cassé la jambe !
(occasional pronominal verb, you must follow the rules of the passé composé with avoir, because you may say "ta mère a cassé sa jambe")
Mme Beaufour- Non, non, ma jambe n'est pas cassée ! Je peux la plier.
(past participle used as an adjective; feminine singular = agrees with "jambe")
Well, I tried to explain my best........
Hope I didn't make any mistakes (even for French, it's not that easy !!!!)
Hope this will help anyway !!