I might let someone borrow my 50 1.4, but some lenses, not even by accident. Even my girlfirend would be out of luck. Well, unless she would let me "borrow" some of her girlfriends.
and not act all jealous afterwords, which would only be fair since I would not act jealous after she borrowed a lens or two.
However, good advice to go with a particular brand if you have (or hope you have
) access to compatible lenses.
She would be "borrowing" your lenses for ....?