I read somewhere that there is an mercant(Spelling) that sells beutyfull stuf for jaheira, but i am whit Aerie and will i can get some stuff for her?

Shame on you: I always felt that romancing
Aerie is like romancing your own baby sister !

Minor Spoiler !
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Btw, the merchant you are asking about is located in front of Valygar's house in the Docks district. I am not sure, but I guess he will sell to you what you are seeking regardless of whom you are romancing. Provided, of course, that he does not share my qualms about romancing minors.

So long,

Ramon