I have a deliema...

My 17 month old daughter has been sleeping in her crib since she was 3 months. We have created such a routine that if we asked her if she wanted to go "night night" she would go climb up the stairs and run to her room saying "night night". We'd give her a small drink and stand her in her crib, she would immediately lay down and go to sleep on her own. This past Saturday, my husband and I went to a friends surprise birthday party/back yard barbecue, and asked my in-laws to come over and watch her. This isn't anything new, they have watched her before. We came home and all was good, baby was in bed sleeping soundly. The next night when bed time rolled around, we did our usual routine, but this time when I put her in her crib, she started screaming hysterically. I left her for a few minutes to let her " cry it out" but she wasn't letting up. I finally went in her room and picked her up. She immediately stopped, said "mommy" in her sad little voice and snuggled in my neck. I tried the whole crib thing again and the same thing happened. I finally caved in after 2 hours and done something I've never done before...brought her in my bed! She snuggled up on my 5.5month baby bump and fell fast asleep. Around 230am I asked my husband to put her in her crib with success. Hoping it was a fluke, we did our usual routine again tonight, again with the hysterical crying. This time I rocked her until she fell asleep, held her tight for a litttle while longer and had my husband place her in her crib (I can't lean over with my belly in the way) I was thinking it is sleep regression but after she's asleep, she is fine. I'm starting to have a feeling that my MIL might have done something like scare her or something that is causing her to be afraid to sleep. She seems to find it funny to hide and jump out at her and scare when playing so it wouldn't surprise me. We asked her if something happened to cause this and she said no, but offered to come take her for the night... umm...no. Was this part of her plan? To save the day and play "mommy" to her? I'm so sad for my baby!