Expected to give discount

I did a photo shoot for my girlfriends sister as she just had her baby. I know her well and we have a good relationship. I gave her a really good price as she insisted on paying. Well now her mom told another one of her family members, who I’ve never even met, that I do photos. That wouldn’t be a problem as that is potentially a new job lead but the problem is she told them I gave my girlfriends sister a major discount and now I feel like this person that I don’t know at all will expect the same discount. Am I over thinking this and should just be okay with it because it’s technically family or am I right to be a little irritated because she gave her the expectation of a discount?