I know a lot of parents hate to let their kids cry it out, but at 18 months she knows what to do to get her own way.
You need to plan on 3 or 5 really rough nights for both of you and peaceful sleep in your own bed after that!
If you are going to let her cry it out YOU have to stick to your guns. the WORST thing you can do is let her cry for half the night then give in at some point. She still sleeps in a crib so you are best to break this habit before she is ready for a toddler bed or before you are ready for a 2nd child. I am a stay at home mom too and I have 2 children a 7 yr. old boy and a 4 year old girl.
My husband and I had 0ne very tough week with both of them when they were that age, but now we see the fruits of our labor. Both kids can go to bed everynight with out a fuss. Usually our bedtime ritual takes 15 - 20 minutes tops.
I know it is hard to hear them cry, just remember that you know in the long run it is best that she is able to soothe herself and fall asleep alone. No one enjoys hearing their child cry but sometimes as parents we have to do what is best even when we don't like it. Remember you are with her all day so you can heep lots of extra love and attention on her during the day.
Good Luck.