Friend asking to borrow clothes, awkward!

[Jiminycrickets]

I have a friend who asks to borrow my clothes. We are both in our 40s, she’s financially secure. She’s a school Mum, so I have to tread carefully to avoid awkward interactions.
I don’t have anyone else in my life who asks or does this! I don’t borrow clothes either. This is something we all did at uni when everyone had limited funds and clothing. I leant her a cheap shirt about a year ago, because I felt put on the spot in a group of people. She returned it clean. But now she’s asked to borrow a very expensive dress of mine and I don’t want to lend it. The main reason is I feel you can always tell when someone a different shape has worn your things and they don’t fit the same. She also could notreplace it if something happened, it’s out of stock.
Years ago, my flat mate borrowed my shoes without asking and stretched them out so much I couldn’t wear them anymore because they fell off. Since then I really don’t feel comfortable with the concept.
How can I say no without making it awkward and also fend off future requests?

If this person isn’t very close to you, I can’t think of any reason not to just say, I don’t lend clothes out as a rule - the shirt was an exception.

As and adult I can think of 2 occasions of borrowing clothes- once when visiting my
best mate and my then 1 year old projective vomited allll over me. I borrowed some cheap leggings and top just to drive home and obviously cleaned and returned them.

The same BF once asked if I had any dresses she could borrow for an event that was sprung on her with 24 hrs notice. I told her she could pick any dress she liked from my wardrobe, because a) she takes excellent care of everything b) if an accident did happen she would be mortified and try to right it in anyway she could - like paying for a repair/ replacement/ professional clean or whatever c) I don’t care about any of my clothes enough to be devastated if something accidental did happen so it wouldn’t have affected our friendship.

you could always tell her you’ve got fleas/ clothes moths/ scabies in the house😂😂. She’d never ask again but it may damage your school reputation!