Hello, dear!
It's okay, we all have different tastes when it comes to clothes. Your mum might not know exactly what style you want to wear, or it might be different from what you expect and anticipate in your heart. It's the same with clothes, when you see them or wear them, they might not feel the way you want them to, they might not be the style you want, they might not match the style and temperament you imagined. And sometimes when you compare the price, you might feel bad about it. It's only natural to have different tastes, and it can sometimes cause a bit of a conflict.
Sometimes, when she sees you and your sister wearing new clothes that really show off your figures, she feels a little envious and thinks that the clothes look really good on you. She'll tell you how much she appreciates the clothes, which is also a kind of appreciation and affirmation for you.
It's so lovely that you get to go shopping with your mum to buy clothes! You can give her your own suggestions and opinions. For example, if you think that this piece of clothing suits your mum's temperament and is also very fashionable, you can praise her for looking good in it. This way, your mum will feel more confident and know what she wants.
It's totally understandable to feel confused and prejudiced when you're shopping with your mom. It's not always easy! Sometimes it can feel like your mom is picking on you, either not giving advice or urging you to make a decision quickly. It's clear that your needs and your mom's needs aren't always aligned. It can feel like you're both talking about your own ideas and opinions.
For instance, you might want your mom to have a firmer opinion, while she might be hoping for your advice and suggestions. You could even help her choose clothes together!
For example, when I bought clothes for my mother before, no matter if I carefully selected the style or if the clothes fit perfectly, she would find fault with them in some way. Perhaps she was used to saying the opposite of what she really meant, and that was just the way she expressed herself.
Sometimes you can figure out what you should do and then just do it! For example, buying the right clothes for your mom is your job, and you did a great job. Then, on the mom's side, there are definitely some limits, and it's not all our fault as kids. Don't blame yourself for everything! This is part of the mom's own part, her own way of thinking, understanding, expressing herself, style of doing things, etc.
You can express yourself completely according to your own frequency. For example, you can buy clothes by yourself or buy your mother clothes according to your own wishes. As long as you do it well, you're doing great! You can also choose a more suitable way. For example, if it's not suitable to go shopping together and buy clothes in a physical store, you can buy them according to your mother's preferences and size style, and give them to her.


Comments
I understand your frustration. It sounds like a tough situation. Maybe it's time to have an open conversation with your mom about how you feel. Express that you want to help but her constant criticism makes it difficult and not enjoyable for you.
It seems like the root of the problem is communication. Instead of buying clothes or forcing her to try things on, perhaps you could ask your mother what she really needs or likes. That way, you can either look for those specific items or know better what to avoid.
The pressure to please your mother with clothing choices feels overwhelming. It might be helpful to shift focus away from material gifts like clothes. Consider spending quality time together doing activities she enjoys or finding other ways to show your care and affection that don't involve shopping.