I echo what Kelly says above, anything we can help with? Maybe just chatting to us on here some more might help you?!
I know that it's so hard to get over an incident, or one where you can only see the worst 'would could have happened' scenarios...
When I first rehomed Archie a couple of years ago, before I got Sonny, I used to have fields on my doorstep... very comforting walking there and I enjoyed going out so much with firstly my old boy Charlie, and then when he passed away, with new kid on the block Archie... Usually if we ever did meet any other dog walkers (not many people had dogs where I used to live either so it was meeting others was usually a scare thing) they were polite, friendly and always had their dogs under control... fab, right!
Anyhow, one day I walked into the top field and stopped dead... at the top of a hill a few hundred yards away was a guy and three of THE hugest rottweilers I have ever seen... all off lead...

Now, rightly or wrongly, and I'm not getting into that debate

I don't like rottweilers, german shepherds, dobermans... they all scare me... so to see 3 off lead put goosebumps on the back of my neck immediately... I didn't even have chance to turn Archie around and go back before they came hurtling down the hill straight at us... I felt sick, still do remembering it now

They surround Archie and it was so strategically done there was nothing I could do.... one pinned him to the ground with its nose/head... one brought up the left side and the other the right, when I tried getting closer one turned at me, growled and positioned its body between me and Arch... talk about helpless
The owner by this time had come huffing and puffing down the hill, and I saw he was a tiny old man... in his 60's easily, smaller than me (and I'm only 5ft3), and wasn't carrying one lead nevermind 3!!

He didn't try calling any of the dogs off by name... and when one started to growl at Arch, all he said was 'now then which one of you was that' in the way you might tell off a kid for letting a pet bunny out of its cage, not one that's got a rolling pin in it's hands and about to bash the bunny's head in!!
He finally just shrugged and walked off and after another few minutes that seemed like an eternal stand off, the dogs one by one followed him... god knows what I'd have done if it'd gone a different way...
I stood where I was until I knew the dogs had gone and walked up the hill (where they'd come from)... there I found a woman very upset, with 2 gorgeous boxer pups... she said she'd just had the same encounter with the same man and dogs and she'd been afraid too that her pups were gonna be attacked (apparantly they left hers alone when they spotted me and Arch walk into the field)...
It took me ages and ages to get over this... but the only thing was forcing myself to get back out there and not avoid the place... Archie needing walking and that was the only place to do it... so 'back on the saddle' so to speak was therapy...
Now, sometimes it creeps back in, when I encounter so many unruly dogs whose owners seem to think it's ok to let their dogs run wild and jump all over other peoples dogs.... esp having 2 and no free hands when they're on lead, I often think of 'what if' they get attacked, how will I end it or cope... but it's not heathy thinking this way and I don't want the boys to pick up on mums anxieties and start displaying similar behaviours, they're incredibly sensitive and maybe Elly is picking up on what you are projecting? putting on a brave face for her sake as a start will maybe help you resume normality, and then as time goes on, slowly you might not have to pretend so much and it will become normal again...
Like Kelly says, getting Elly out and about socialising with other friendly dogs is perfect to help her understand not all dogs are like this...
After Arch has been yet again jumped all over by strange not-on-lead dogs today, I've made us a play date with my best friend and her dog tomorrow for walkies together... Arch can play and frolic with his pal as much as he likes, and vice versa... and it helps encourage and define the difference between dogs that come racing towards him unexpectedly in the park growling and teeth barring which cause him to go submissive, and ones that he can play with and stand up to and build his confidence with...
What I'm trying to say is I'm sure we've all had a truly awful experience with our pooches where we've been a wee bit worried, but you will get through it and out enjoying your walks again in no time... Don't let one irresponsible dog owner upset you for too long, she's not worth having this much of an effect... she may be keeping herself way away from that area now realising you would have reported her, so you may never find her again!
If there's anything at all we can do to help, please just holler!!
Sounds like Elly is a very brave girl and will come through just fine... and am sure her mum will too
tinks x