May I ask why do you want to breed her? Is the reason financial or
emotional? What will you do with the kittens? How often will you breed her?

Gee

Do you belong to a Cat Club?
I suggest you get in touch with one, or GCCF if you live in the UK to ask
about a good stud owner, Breeding is a very expensive and complicated
business to get into!
most breeders keep their toms as closed Stud, So you may have to travel,
then the upset can stop your cat from calling! it is expensive to have her
mated, about ?250.00... then she may not take, so she will need to
return.... some let them return for free some don't.
you have to check your Queen is healthy and have a snap blood test done
before mating, and all inoculations are up to date. These records will be
asked for by the stud owner. Also make sure the stud you take her to has
been tested.
You should  visit the studs home before hand to make sure it is a nice place
for your cat to stay, she will probably be there a week.

I should do a Google Search under Siamese Breeding etc..... you should spend
a great deal of time, researching, the expense, care needed and vet bills.
Things like..... Supposing she has to have a caesarean?  she may not feed
them herself so you will have to do this New-born kittens need up to 10
feeds in each 24 hour period, and if you had 6 that is real hard work! so
not for people you work outside of their homes, and trust me kittens don't
just suck from a bottle, normally you have to syringe feed them drip by
drip, they need weighing before and after a feed!

Heating, Kittening box, place from them once they start running around? you
can't have baby kittens charging around all over your house, it too
dangerous for you and them.
A first aid box, I could go on for ages adding! :-)

There is a great deal of pleasure in raising kittens, but many sleepless
nights, time and expense.  I spent about a 2 years reading and learning,
then there is the selling point! its very difficult to find people who you
feel totally comfortable with buying your babies! you get plenty of response
but most of them I wouldn't sell them a toy cat! let alone a real live
kitten, who I am responsible for!

There is tons of information out there, I buy & loan books, search the net,
buy magazines, ask other breeders. I also belong to 2 cat clubs, attend
meetings, shows to get advice from breeders. But I have enjoyed it, and knew
it was the right thing for me to do, and my family of course because they
need to kitten sit when I pop to the supermarket!

Hope this helps