No the run cannot be included if they are to be living outside full time during the summer.
The hutch is the only living space and needs to meet size requirements (the run is not living space). They cannot have constant access to the run.
The hutch part itself needs to be 180x60cm (6ft x 2ft) to be big enough for three piggies to live in.
If they lived indoors in the c&c year round but were only put out into the run during the day (supervised) for exercise then brought back indoors at night, then as long as the run is big enough, the hutch size wouldn’t really matter as they would not be shut into it - the hutch would effectively just be a shelter for exercise time.
It would be safest for you to take your girls to a rescue centre to find them a new companion. Adding a single sow to a bonded pair is not always straight forward.
If that is not possible, then ensure you have a plan B for separate living arrangements should the bonding fail and she isn’t accepted into the pair.
A neutered boar can be more easily accepted by a bonded pair of sows.
Adding More Guinea Pigs Or Merging Pairs – What Works And What Not?