I have a half sister, she's married and lives 8 hours away from my home in a very small town.

I have a 'family friend' relationship with her, since she's my half sister and we didn't grew up together; She's a really sweet lady.
Today she asked me to go and buy a dress for her in her friend's store that is 2 hours away from my house. She has an event soon and she wants a new dress

The thing is, I'm very busy with my thesis and my job and I don't have that much time to spend half a day to get her a new dress (I don't have a car and I'll take the bus); she already has a somewhat new dress (the one she wore at my sister's wedding this last september in my town).

I'm a very anxious person, so this situation is difficult for me to know what to do. My sister lives 30 minutes away from the dress store, I can't ask my sister to go and buy the dress for my half sister since I don't talk to her, so I don't know exactly what to do. Also, my mother is a dressmaker and she offered a few dresses to my half sister to choose. My half sister didn't like the dresses.

It is selfish not wanting to adjust my schedule to go? How can I politely say no to her?
user
Sister wants a new dress, so I'm busy. She asked me to go get her a dress from a friend's store 2 hours away from my house. I don't have time to go and buy her a dress
assistant
I have a half sister, she's married and lives 8 hours away from my home in a very small town.

I have a 'family friend' relationship with her, since she's my half sister and we didn't grew up together; She's a really sweet lady.
Today she asked me to go and buy a dress for her in her friend's store that is 2 hours away from my house. She has an event soon and she wants a new dress

The thing is, I'm very busy with my thesis and my job and I don't have that much time to spend half a day to get her a new dress (I don't have a car and I'll take the bus); she already has a somewhat new dress (the one she wore at my sister's wedding this last september in my town).

I'm a very anxious person, so this situation is difficult for me to know what to do. My sister lives 30 minutes away from the dress store, I can't ask my sister to go and buy the dress for my half sister since I don't talk to her, so I don't know exactly what to do. Also, my mother is a dressmaker and she offered a few dresses to my half sister to choose. My half sister didn't like the dresses.

It is selfish not wanting to adjust my schedule to go? How can I politely say no to her?
user
Half sister is very busy and I don't have much time to spend with her. I can't afford to go to her friend's store in order to buy a dress for her, but she wants to buy a
assistant