She is determined. We've had to be really carefull with the upstairs windows as she's trying to squeeze herself out of the smallest gap and I can see she's trying to jump up and open the French doors so we've had to start locking them.
Best of luck. And if your vet won't budge, best develop eyes in the back of your head for a few weeks. They can be right determined when they want to go out and 'meet' and you may think that your garden is fully enclosed but unless it has 12 foot walls, she'll find a way.
4-5 months is old enough, I'm afraid. I'm not too too worried about her getting pregnant because the spaying would take care of that (unless she was very advanced) but they can become stupid when they see a handsome bit of stuff across the road - and your cul de sac might seem quiet but they can actually be quite dangerous because the cats aren't ever-alert for cars.
I'd tell your vet that she's yowling to get out in mid winter and see if you can reach an accommodation with them.
My kitten is 19 weeks old now and fully vaccinated and chipped. She's due to be speyed at 6 months as my vets won't do younger than that as shes onl a small cat - she's a petite tortie girl a a little over 2kg.
For a last couple of weeks I've been taking her in the garden with me when I hang out the washing etc and she loves it .. A little too much maybe as now she spends a fair amount of her time pitifully yowling at the door and trying to plot her escape. Yesterday we had guests and she got out the front door and had to tempt her back with dreamies. We live in a fairly quiet cul de sac and have a fully enclosed garden. No cat flap.
What is the best age? Is now ok or sould we wait till after speying? I have never had a cat before and advice on the Internet seems to vary wildly.