Speaking as a family who are prone to sprains and strains (hypermobile joints). Torn ligaments can be agonising for weeks. DD was still on ibrupofen/paracetamol round the clock and applying ice packs at this stage.
Those microwaveable wheat bags put in the freezer are better than cool packs. They mould to the body better and don't get too cold but hold the cold for a long time. 10 mins max
If you can keep walking without crutches that's better but otherwise yes definitely to crutches. Explain it is to help her weight bear, not so she can swing her ankle through. SHE MUST WEIGHT BEAR this is so important but there are some (very very rare but just so happens I have had) complications that can be avoided by continuing to weight bear and it reduces muscles loss (which is important for holding ligaments and tendons in place). It is easier with crutches as you start with just putting the foot to the floor as you walk but taking most of the weight through your crutches.on a particular bad injury at a two weeks I was still reminding DD of the need to do this and not swing the leg through as she found it very painful. Only at four weeks I had removed the crutches from her since she didn't need them but was nervous to do without. But it took this long for her to full weight bear. Healing sprains is slow and isn't easy, but the more you can keep it moving (on land or water) the better.
Dump the tubigrip (what doctor is still giving out tubigrips?!?! They do nothing literally) in favour of kinesology tape. It's what the athletes use and it's aim is to promote active healing. It helps hold the ligaments and tendons in the right position while they heal. Ime it is incrediable stuff and may provide the necessary support your DD needs to get foot to floor and walk on it. For ankle you need roughly forearm length straps wrapped under the foot crossed on the top of the ankle and run up the leg. Basically dping the job of a tendon. You can search kinesiology tape ankle injury on you tube but not one that mummifies the ankle, less is quite definitely more. ( If you actually get one) your NHS physio won't approve and will tell you off (they want you to full weight bear regardless), but a private physio will be doing it for you. If you can afford to get to a good private physio it is worth trying to do.
Watch out for repeat injury after. If at 2-3 months you find your DD is still failing over and twisting it on a semi regular basis, at that point she absolutely needs physio. NHS is fine but will take a while (3 months in our area). Private better because it is quicker. We have used both depending on finances.
Add another 6-8 weeks recovery time everything it twists again. You really want to avoid this so its worth thinking about shoes!!
On shoes it will be sensible shoes all the way for a while... She will find something like memory foam trainers easier at the start (they absorb some of the impact of the heelstrike reducing the pain of getting the foot down) but they don't really offer a fantastic level of support. At a barest minimum, something with a decent heel cup (think the footbed of a birkenstock) so the ankle and foot is held in the right position, and a way of securing it over the top. She may find long walks quite sore for quite some time after and that when it's tired it is more prone to twists and turns. You want to support the ankle well to prevent this. I found it a tug of war with DD over the demands of peer pressure etc, but if she is walking any distance she will wear dr martens all year round and (after a few shoves in the right direction by physio) will now wear kickers for school. DS wears kickers almost full time. I wear Dr Martens and ankle walking boots if I am walking anywhere with uneven ground. Mostly I can get away with decent sandles on the flat in summer.
Good luck and she has my sympathy. It's miserable.