Oh dear, poor Liz! There are so many instances where people have bad luck but with a fractured hip it's almost inevitable. I don't see if you live in US or UK but I can tell you what I know about this, if it helps.
First off, unless the fracture is inside the joint (subcapital fracture) it's very uncommon for the surgeon to proceed immediately to a replacement. It's just not an option. The reason for this is that there is a very good chance the fracture will heal and everything will be alright. Rushing into a THR is not a good protocol as the fixation you had does not require the hip joint being entered at all and is a much lesser procedure. It has a lesser chance of traumatic arthritis developing as a result of surgery. I say this because had the fracture been inside the joint, the option would most likely have been a hemi-arthroplasty or replacement of the head alone as the cup part of the joint, being in good condition, does not need to be interfered with.
The age factors into this for two reason, first because it means you have a very good chance of it healing well and secondly because you are a tad on the young side to have a THR.
But there are some other things you should remember. First, you are only 8 weeks post op. Fractures take around 14-16 weeks to heal and in the hip, maybe a bit longer. Second, this was as the result of a bad fall which in itself takes a while to recover from and will inevitably delay the healing process.
Third, the prediction that your present hip will 'only last four years' is just that, a prediction, a guess-timate and by no means a certainty. With any luck, it could last much, much longer than that. At this time, nobody knows how long it will last. If you had the usual Dynamic Hip Screw fixation (DHS), they are actually a very good appliance and, unlike the static appliances used in my young day, can adjust to any bone adsorption (shrinkage) that will occur around the fracture site.
So, my advice to you is to try to be more patient. Nothing goes quickly where bones are concerned nor is anything carved in tablets of stone. You may/may not require a THR at a later stage but don't rush into it. You do not yet know how well you will do with this. Give it time. You might be surprised.