For lack of recall get her on a long training lead, not an extending lead, attached to a harness, not her collar.
Put knots, not too close together, along its length and you can leave it trailing, unless she's likely to bolt completely, in which case she has to stay on the lead.
The knots are so you can stamp on the lead to stop her when she's not letting you get hold of her.
Other than that, as pps have said, it will pass. Just keep on reinforcing the training you've put in place up till now.
Don't tell her off when she comes back to you, no matter how long it takes - and the trailing lead will make getting her back easier - just don't react in any way.
Try recalling her, and when/if she does come back, touch her collar and then let her go again so coming back doesn't mean the fun times are over. Also become the most exciting thing in the park: lots of jumping and running and a high pitched excited voice, hide and seek games, that sort of thing.
Make yourself more interesting than anything else she might be interested in.
If her recall is completely shot, she can't be allowed to be off lead and free to run away, which is why the training lead is worth a try.