Follow the bonding guides on this site, they will provide you with all the information you need on how to do the bonding - the best thing is to put the new girl in a separate cage next to your current girls cage for a few days so that they get used to the idea of another being piggy around, neutral space bonding pen, make sure the cage that all three will live in is fully scent free (you don’t want your current girls to think the new girl is an intruder), putting them all back in the same cage together after theyve been in the bonding pen. Remember that even after the initial introductions, fully bonding can go on for a while longer - weeks sometimes - so you may continue to see dominance behaviour for a while after. Check your cage is definitely big enough for all three piggies (‘cage size guide’ is on this site) as lack of space is a good place to start with a fall out! Ensure you’ve got enough food bowls etc, open ended hideys so that no one piggy can get cornered. Also read up on what signs you are looking out for which show the bonding is working or warning signs and when to step in - don’t panic and step in a separate too soon as if you then put them back together, they’ll need to start all over again and if is stressful for them.
Good luck with them!
