Firstly, I would like to applaud you for your attitude to your life. At the age you are, some people have lived with bad habits for years, that become entrenched and they get very bitter, negative or defensive, of being told they need to change, as if having a "cheat death" kind of approach to living, hasn't come home to roost in earlier years, so why should they change and do things potentially perceived as reducing their satisfaction in life.
Your attitude is stirling and I admire you for it greatly
In relation to becoming stagnant with training, simple variations may sometimes be all you need. Biceps have so many variations it's easy to chop and change, Back exercises, you can change a row exercise from Cable to Barbell in nature and vice versa. Triceps can be switched from a standing exercise to a bench based one and even subtle variations on a theme, like say normal Deadlifts versus Romanians, E-Z Bar Curls versus, Reverse E-Z Bar Curls, standing Cable Rows, versus seated Cable Rows.
So the options are there and if you're not really someone that wants to use a "system", like pyramid, drop sets, tri sets etc, then there is no need, because using variations or like for like exercises, can make things seem different.
The only thing I would advocate is keeping the structure, so whatever sequence of bodyparts you train on a given day, keep that sequence. I used to use spotters vary sparingly in the past, but I don't do it now, because I don't do anything that requires one, so I can understand your stance.
The main thing with what you said is not going heavier if you don't use spotters, becasue with some exercises, you could chance it, if you were 50/50 about being able to go a bit heavier, but if it was an exercises where you are pushing weight above your Chest or Head, or resting it on your back, then that's too risky, but on a standing free weight exercise or standing / seated machine based one, for the upper body, the risk can be taken, because releasing the weight too soon, shouldn't risk injury to yourself, unless the weight accidentally slips from your grasp, as opposed to an intended release.
Hopefully what I said makes some semblance of sense and gives you something to consider, but whatever happens keep on pushing and keep on believing, because you should be extremely proud of yourself and your fine example to other younger females and also to men too, because you have shunned the kind of lifestyles, many had 50+ years ago, that are now known to be far worse than was previously thought, when like so many of your generation, you could have become a long-term casualty, of adopting the ignorance and plain laziness towards wellness, many in that society practised daily
If you need any more help or assistance regards anything, or would like to share some of your wisdom and inner self with us, please do visit us as much as you wish, because we would be more than happy to have you as part of our site.
Your example has definitely humbled me and I wish you a lot of luck and happiness with your contineud goal
I can only hope in around 30 years from now, when I'm practically your age, my resolve will be as steadfast as yours is.