When my Siamese was ready to have her babies, she started meowing like mad! She wanted me to be right beside her wherever she went and showed me her nesting box. Mimi didn't have milk coming from her nipples, so I thought she wasn't ready to have the babies. She lost her mucus plug which was a surefire sign she was ready. Mimi was in the first stage of labor for almost 10 hours, then all of the sudden she started having contractions! Pop! There was a precious black kitten! Mimi had 4 kittens, but sadly, on passed away.
It sounds like your kitty is in the first stage of labor. Is she showing any nesting signs? Such as digging at blankets, newspaper etc.? My friend has a Siamese who had her babies breech. I delivered both of them, although she probably could've done it on her own. Good luck with her labor, and please keep us updated!