First egg, lots of problems

Our hen Sadie is just shy of 20 wks, one of our 4 oldest pullets.  Her sister Maggie began laying 6 days ago, pretty normal scenario with her - instincts kicked in and she was good to go.  Sadie was free ranging tonight and I noticed some clear stuff dribbling from her bottom and she wasn't acting herself.  Panting, wings out to her sides and sort of hobbling.  I imagined the worst and picked her up to examine her.  I cleaned her vent and the liquid off with a baby wipe and she immediately strained with about a dime size amount of an egg showing.  I took her into the coop and tried to get her into a nest box but she didn't seem to have the instinct.  She was panicked, and wanted out.  She strained and strained for about 15 minutes out in the corner of the run;  finally laying a soft shelled egg and then a fart egg which was also shell-less and appeared to be just a yolk with a membrane.  She stood still panting and crouched for a few minutes after, no egg song.   She didn't prolapse thank goodness but I'm concerned about her rough start.  In your experiences, if a hen has a bad start like this does she become a trouble prone layer?   She's a RIR if that has any thing to do with it. 

Thank you both!  This morning her sister laid her egg and I took sadie in there and showed her the egg in the box.  She eyeballed it, chattering to herself and picking at the nest for several minutes and it's like all of a sudden it clicked.   She went in and sat on a nest box for quite some time.  Sang the egg song twice, and I watched her fluffing the nest and tossing shavings behind her and cuddling our fake golfball egg.  :)  She didn't actually lay but I didn't expect her to after laying two yesterday.  The EE's are sneaking around and fluffing the nests as well.  I'll be thrilled if I get some blue eggs this week too!