Hello, and welcome.
I'm so sorry mittens injured her leg.
The best next step for you at this time, is to have her seen in person by a vet, right away. If your vet is closed now, bring her to the nearest ER vet center, where she can be x-rayed, necessary, so you can get a definite diagnosis and she can be treated and given pain medication.
For the moment, try to keep her immobile in a crate or carrier.
Unfortunately, there is no way to fix this at home,nor to determine if it is a break or dislocation. The vet will need to feel it in person and as I mentioned, imaging may be necessary.
If you're in a financial bind, try applying for Care Credit, which is accepted by most vet offices, or bring her in to a VCA animal hospital, which offers free first visits to new patients. They are open extended hours and have offices nationwide, so I hope there's one near you.
I hope all will be well with Mittens! Please keep me posted on how she's doing and what the vet's report is. Thanks!
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