Making dolls clothes sounds like fun and is educational if you just stop to look at it.
There is maths in measuring and there most certainly is art and design.
She will be engaging in creative play with her dolls in their new clothes, which could be seen as creative stories.
She will be problem solving and will be developing psycho-motor skills including hand eye communication.
You could see if she is interested in looking at the history of costumes and how fashion developed and go along to museums and maybe find some historical reanactment days to attend, and look at all of the costumes.
You could look at the practicalities of the costumes, how the cloths were made through the ages, how the colours were created and spend a fun day doing some tie-dye! (but only for as long as her interest lasts, you don't want her to go off it because you take over and make it too schooly-a mistake I am ashamed to say I did at the beginning!)
One of my daughters was always interested in womens rights and would always be interested in anything to do with it, and so womens costumes, role in the home etc was always a good bet, for interesting her in history and politics and fashion design, and, and, and ......
A blog would be great and she could post pictures of the things she has made.
Talking about everything and anything she is interested in is IMO the most efficient way of educating! You are doing so on a one to one basis and can correct any misunderstandings immeadiately and encourage her to stretch her thinking and ideas.
For what it is worth it took me and dh a hell of a lot longer to get out of the mind set that education means sitting down and being taught and doing 'work', than it ever did the kids!
I'd carry on exactly as you are and you'll look back with great suprise when you see how much she has learned in 6 months time with out any formal work at all!
In the meantime Alan Thomas wrote an artical on 'Informal Learning' it's quite old now but still relevant I think, and it might alsa be worth reading his book How Children Learn at Home