Hello T.,
Here are some ideas that are worth a try. You may have tried this already. Here it goes:
---sounds that might spook her---
if you're playing music while she sleeps... listen to the whole cd! I figured out that the cd I was playing for my son had 'heart beats' as one of the 'songs' and that always woke him up... about 45 minutes into his nap!!!
and believe it or not, by this age... there are songs she doesn't like...
---worn t-shirt w/ your scent---
Wear a t-shirt a couple of nights in a row, then when you lay your baby down for a nap, put it near tne crib (of course, being careful that the t-shirt won't fall on the baby, etc). The t-shirt will have your scent. maybe that will give you a bit more time.
---watch what you're eating (or not eating)---
if you're breast-feeding... the coffee/soda you drink will affect her too.
---your husband's scent---
maybe his cologne/aftershave is too strong for her little nose... for your husband... have him take a shower w/ no soap -- no after shave,lotion, etc. have him hold her along w/ your 2-night-worn-t-shirt.
also have him sit next to you on the evening feeding and perhaps she'll get used to him holding her. and if you're using bottles, have him hold the bottle and little by little work on him holding her during the feeding.
---your soothing voice---
massage her hands, arms, feet and legs. record some stories, songs and put it on a cd... play it for her while she sleeps and while someone else is holding her.
---aromatherapy & relaxation---
on the aromatherapy note... are YOU feeling OK? if you're restless, she'll pick up on it and will want you to hold her even more. I know I'm sort of making assumptions here but I'm hoping that any of my ramblings may help you. so get some soothing music and some lavender oil put on a funny movie and relax a little. put a few drops of lavender oil on cotton balls and set them on the table ..actually forget the cotton balls -- get a paper towel, fold it in half and put 8-10 drops of lavender oil on it and put it on a plate and enjoy the air.
make a list of the things you enjoy the most and see if you can do one for 3-4 days in a row.
with 4 other kids you must be pretty busy too. do you need help w/ carpooling? can the 14-y-olds prep dinner?
good luck!