Dear Rabbi, if you are walking on the street, about to enter your building and see your old non jewish neighbour walking along you,also about to enter the same building, and having difficulties to carry her bags on Shabbos. Out of pure politeness and kindness action, would you be able to help her to carry her goods? thanks.
With all due credit to your good will, you should refrain from helping. Although, you are in the building and not in a public place there are still issues of taking something from somebody who was in Reshut Harabim which may complete the "melacha" of moving things on Shabbat from one domain to another domain. In addition, there are issues of muktzeh which may be in the bags. Muktzeh is not necessarily electrical items but also raw potatoes or flour which are unfit for use on Shabbat and are considered muktzeh. Should you have a guilty feeling for not helping, I think when your neighbor sees you in your Shabbat clothing she will realize that this is not the attire they expect someone to help them with their bags.