Try not to stress about it! I was the same as you- Mo (the ginger piggy) had been alone for around a year before I brought Steve home. Mainly because he had a health scare and the first friend I had for him sadly passed away. I introduced them straight away (first time binding it was a bit scary) and luckily Mo accepted Steve with open arms! I'm going to tag two threads that may help you- the first thread is when I bought Steve home and the second shows you what I saw.
Remember that during binding you should expect to see:
1- mounting
2- rumbling
3- potentially nipping or raising their heads
4- chasing
5- noise!
Please try not to separate unless there is blood drawn or you feel a piggy will come to harm. Remember to do the introductions in a neutral space with a nice pile of veg.
Both my boys are from a breeder who lives locally and I took a risk introducing them straight away instead of waiting and luckily nothing happened. I did trust the man whom had raised them seeing as all my pigs (Vinnie,Mo and Steve) are from him. I have known people who gave got their guinea pigs from such places as Pets At home and introduced them straight away so if you feel she is healthy then you can start bonding.
One last thing- please do double check the gender. That is the main thing pet stores mess up on. You don't want any baby pigs lol.
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Videos To Help Those Who May Be Thinking Of Bonding Guinea Pigs.