Well, what can I say. I love Ysolda :D I'm sure I'm not the only one. Of course this "mod" isn't a big thing, but this is my first mod.
Please click on ENDORSE if you like it = )

Features:
- small changes in her appearance (stayed at Vanilla, no other mod needed)
- added sneak perks (Stealth, Muffeled Movement, Light Foot, Silent Roll, Silence)
- instant marriage support (works only if you have not done her quest yet - check solution below)
- instant follower support
- auto level up (she will level up according to your level)

If you've alredy done the quest she gives, you can use a console command to make her marriable:
first click on her so her ID appears in the console, than type:
addtofaction 19809 1

Install:
Just simply unpack "Sweet Ysolda.rar" into your Skyrim/Data folder
Don't forget to activate it in your mod manager or Skyrim's launcher (at Data Files).

Issues:
If her appearance doesn't change at the first load, Save game, Quit and Load it again.