Ok ill try and answer as best I can.
"Ive read on the internet that i can house 3 dragons in a tank that size but was thinking about just getting her 1 cage mate. "
Not sure where you read that, but I can tell you know it is strongly frowned upon on this site. They recomend 75 gallons for ONE dragon here. 40 breeder is the minimum that you shoul be using.
Also BD's are solitary animals. They do not like company. They like to have their own territory.
"My first question is does the sex of the animal i put her in with matter? If it is a boy will they breed? If so what would i do with the babies? "
Yes it definetly matters. Males/Male is a big no no, constant fights which could lead to the dath of one of them by starvation, stress or jsut being killed by the other. Male/Female is a no no as well, they will try and mate eveyr chacne they get. And then you have babies, which you will have to incubate, then feed and house until you can get rid of them.
Female/Female is probably the only chance you would have for them living together. Even then youd have to watch them closely.
"Another question is does the size of the dragon i put in with her matter? "
Yup, most definetly. Only house two of the same size dragons together. Could definetly lead to bad health/death for the smaller one.
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2.0 Ball Pythons (Kurt the Snake ~ Frosty McFry)
0.1 Leucistic Texas Rat (OogieBoogie)
0.1 Kenyan Sand Boa (NoFingers McGee)
1.1 Bearded Dragons (Saku ~ GracieJ)
0.0.1 Albino Ornate Pacman Frog (Jabba the Frog)
0.0.1 Ornate Pacman Frog (Hooter)
0.0.1 Emperor Scorpion (Still Thinking)
0.0.1 Usambara Tarantula - (FBD - Fire Ball of Death)
2.0 House Cats (Bill ~ Ted)
And a partrige in a pear tree...
~!Bearded Dragon Custom Cage Design!~