My Cat Mittens!?!?!?!?! For People who care for long questions and are willing to read it!!?!?

My Cat "Mittens" is a outdoor cat. But she's always inside now.. She's been in the house for about 3-4 months... She's turning 1 on April Fools Day.. Now for the question. Do you think I can Trust her for the magnetic collar? ( it opens cat door ) Because this is the first time I owned a cat.... and I'm using my friends account so don't argue about the age! Im 10 so... And Another Question! Do you think i SHOULD use it? For a cat thats turning 1 on Aprils Fools!? Sorry for long question Everyone! I just want my cat to be safe and i dont know what to do! I even have a big doberman dog named Fritz :P they hate eachother! Sorry again for long question!