It is interesting to analyse the way that Lady Capulet and Lady Montague are presented in Act I scene 1 and how they are positioned vis-a-vis the feud that dominates their families so much. Both of them are shown to not support or not be a part of the feud. Lady Montague physically tries to restrain her husband from entering the fray, and in the line you have quoted we see how Lady Capulet makes fun of her husband, saying that he is too old to fight, and should be calling for a crutch instead of a long sword.
This quote thus shows that Lady Capulet has a sense of humour but perhaps also we see her biting sarcasm as she, absolutely fed up with the fighting between the two houses, ridicules her husband to show him how stupid he is being. This clearly indicates her strength of character and her own feelings.