Hello, I'd like to help you with your question. It sounds like your girlfriend feels very overwhelmed by the responsibilities of parenting. Some people have the temperament to be a parent and the energy to deal with the high demands of an active child. However, there are others who find the day to day routine, lack of breaks and constant attention needed to cope with a toddler just too much. There is nothing wrong with that, it is just a matter of what one person can handle compared to another.
Although your advice to her is correct and appropriate, it may not be what your girlfriend wants to hear. She simply may not be able to listen and incorporate your advice into her parenting style and therefore becomes upset instead of relieved. What you may want to try is to just listen to her. Sometimes people find great relief in just complaining or expressing their feelings to someone who doesn't say anything or very little at all. It can be very difficult to sit and here all of these distressing emotions from someone and not say anything (particularly if you are studying psychology and have a deeper understanding of what is needed) but often just having someone listen helps the person get the emotions out of their system and reduce their stress.
You may also want to find ways to spend some time alone with your girlfriend. Hire a babysitter and go out or buy dinner and eat together with candlelight after your little one is in bed. If you have the time (it sounds like you are quite busy), you may also want to take a day out with the child so your girlfriend can do something on her own. Just having even a few hours to herself might be enough to recharge her.
And anytime you can provide relief to her, even if it is sometime later in the day or the next day, it can give her something to look forward to so she can handle her stress better.
Also, it may help to remind her that this is a difficult stage of development but it will not last forever. Some time very soon the child will be in school and your girlfriend (and you) will have more time to be on your own and develop other interests outside of parenting.
Unfortunately, because your girlfriend has left behind most of her supports, she only has you for now and that is a lot on you. She may find some benefit to joining a Mommy and me group or something similar to reach out to other parents for support. The more she can socialize the better she will feel and the less she will depend solely on you for help.
I hope this has helped you,