Firstly, I would say that you want to approach the subject in a calm and non-confrontational manner. Despite her recent hesitations towards her relationship, she will still most likely not take external criticism well. Likewise, I would pick an environment that is not her house or uni; possibly even a place that’s meaningful to your friendship or group of friends.
You should reassure her that you’re not vying for her to break up with her boyfriend but merely reminding her that there is a life beyond her relationship and that taking care of her own well-being and education will actually make their relationship stronger and less codependent, as they re-learn to be individuals.
Nonetheless, this is easier said than done as she may not instantly take this information on board or once again be defensive about the relationship. If so, taking a less direct approach may be more beneficial - you could organise a ‘girls’ night or a cocktail evening and without explicitly bringing the topic of her relationship up; try and remind her that her friendships can be just as fulfilling.
However, in regards to the abrupt PDA and “the being Pookie”, a definite conversation needs to be had. If your friend does not want to change her relationship or behaviour then that is up to her, but you are well within your rights to ask her to tone down the PDA in communal areas. It is your house too and you’re paying to live there as well, you deserve to feel comfortable in your own home. As such, I would suggest having a friendly yet firm conversation about it.
Overall, while this kind of situation is never ideal for anyone involved, I can assure you that eventually your friend knows that you’re all there for her and want what is best for her. But she most likely is struggling to come to terms with what needs to be done to either fix or end her relationship. When a person gets into a routine or a certain set of behaviours it is hard for them to break out of it but it is not impossible, and with your support, I am certain that your friend will return to the person she was before.