My cats like to go out in the snow to play so I wouldn't worry.  Most
animals, including cats, put on a thicker coat of hair in the fall for the
winter and loose it in the spring for the summer.  If the cat feels cold she
will curl up on a bed, carpet, in a cardboard box or other 'bed' type area
and go to sleep.  FYI cats have normal temperature of 101.5F.  You could put
a couple of bath towels in a cardboard box or bed if she has one and she
will tunnel in an among them for warmth if she feels cold.

The first Fall cool snap has settled into the SE Texas Gulf coast, and I
made sure my outsiders had a fresh supply of stuffed Xerox boxes to sleep
in.  There are about ten who hang out regularly on the manor grounds, with a
handful of stragglers passing through from time to time.  There is always
food and water--and no dogs to chase them.

I have 15 dry boxes--all setting in protected areas away from wind and rain.
It is not unusual to see a pair of cats in a single box.   In another six
weeks their fur will be noticeably longer and thicker, preparing them for
the upcoming winter.

One big guy has his special padded chair which sits just inside the tool
shed.  He typically shares it in cool weather with a small female whom he
seems to have adopted a few years ago.  Both are fixed--as are all my cats;
so there is very little territoralism present in the group.   Louie, my
little long-haired white guy with a gimpy front foot, has his preference
with one particular box beneath a weatherproof A-frame.  I saw him in it
this morning when I went out to feed everyone.  He took his time--not
wanting to leave the cozy bed.

As for my inside guys, they got their first glimpse of the heating pads
which we took out of mothballs and spread around various places.  They
recognized the pads from previous winters and wasted no time warming their
toes.  When the cool snap retreats and warm weather returns, we'll put the
heating pads away until they are needed again.

--Catmandu

Leave the computer on - she might sleep on top of it.  While my cats
mostly come in when it's below about 50 degrees F outside, many of
them also go outside when it's not far above zero.  Below zero and
they are pretty much all inside.

There will certainly be microclimates in your house where she can go
to be in a place where there is no draft and her body heat is trapped
- maybe under the bed covers (a couple of mine crawl between the
sheets when they feel cold).