A crisis is when you find out eh your TRUE friends are.
Those of us long in the tooth have learned this the hard way usually.
On the plus side you also find that people you previously thought of as "not as close" or even "acquaintances" often step up and are brilliant.
"They have form for selfish behaviour which I've always let slide previously due to length of time I've known them." So you knew what they were like really. Being a friend for a long time doesn't necessarily equate to being good friends.
There's also a quote that stuck in my mind from an old sitcom as it's very true. The storyline was the dad catching up with I think an old college friend and the guy was a bit of a douche and did something out of line and the dad was trying to justify staying friends/letting it slide by saying
'but we've been friends 20 years'
and the wife responds 'no you were friends 20 years ago there's a difference' (not exact quotes can't find the scene).
As you get older you need to learn the difference between good friends, old friends and not really friends.
"Tbf I wouldn’t really think that a broken ankle in an otherwise healthy adult would mean they’d need people round to look after them?" You ever had one? Severely restricts mobility which makes everyday tasks difficult PLUS the body is using more energy than usual to repair the damaged parts. Broken bones can make otherwise healthy people run down and more vulnerable to infection, plus it's just more tiring farting around on crutches! A limb being out of action puts a lot more strain on the rest of the body. That is a NASTY injury and will have taken a lot out of op, she's likely still in quite some pain too.
"If you were seriously ill that would be different obviously" this is a serious injury - impacts a great deal on the patient.
Op as your partner is in the forces are you near to their base? Generally welfare services are only offered to spouses but sometimes they are willing to help if you're not married. It's quite a close knit community, if any of his friends/colleagues are about they might be able to help with eg fetching shopping or meds, putting items in easy to reach places for you.
The sheer lack of understanding/empathy from so many posters on this thread is shocking!
I don't think op is at all unreasonable in expecting who she thought was a good friend who SHE has been there for in tough times to AT LEAST take a genuine interest in how she's doing. A phone call only takes 5/10 mins that is not a big ask.
Yanbu to say to her you're hurt at the lack of compassion at a difficult time, but then I'd take it as "now I know what she's really like" and distance myself massively and not do her any more favours. That's the natural consequence of being a shit friend.
"It’s unfortunately not an uncommon reaction to illness. It does kind of separate the wheat from the chaff friend-wise" absolutely!
"All the people here saying to the OP she is being needy and a victim and selfish and needs to get over herself

are showing what poor friends they clearly are themselves." Totally agree! Glad they're not my friends!
Your update re Xmas market - your "friendship" is sadly all about what SHE gets out of the relationship! YOUR birthday YOU'RE injured and she won't even consider a compromise?! I'd fuck her off at this point! She's not a friend