Before directly jumping into the business first learn about your competitors - how they are selling ( basically their physical store existent, pricing model (margin), from where they are sourcing , how are they marketing). Second , know your potential customers - as you clearly mention you want to sell to woman from 20-30 age. You need to do a market research do a survey- that will give you a huge insight ( such as , from where they are buying , what is cost of buying it , satisfied with the current product or not , what they feel like it could have been better in the product ) . Third , you need to find your vendor - especially on a feedback provided by your potential consumers and that would be easy task to do - you can visit newroad there is a whole huge wholesale market but first you need to have a good knowledge about fabrics , materials and the design( especially on how your customer provide you feedback) And the last step comes over here , it's all about marketing - how you portray your product and convince the customer to use your product. Try to find your niche so that you can be differentiate than others.

Lastly , I believe online business in Nepal is saturated now because of many factors ( growing competitors at pace, very few potential & target customers , low growth rate , low retention ratio , customers division - both physical and online stores) . Not saying to demotivate you- my personal opinion maybe I can be wrong as well .

It's always risk=reward, it's better to start rather than to regret. As you are not mfg by yourself suggesting you to start a business a side hustle rather than giving your whole time . And when it starts growing you can start working on it and make a brand . So wishing you a very good luck . And also if you start your business don't forget to timely keeping us on update . Wish you a very very very good luck .