Wow. If this started when the baby came - or when you were pregnant - it may just be that mil is overly excited. (Is this her first gc?).
Also, people often advise mils to cultivate a friendly relationship with their dil if they want a relationship with their gc. Some even give the well-meaning advice to 'treat her like a daughter." Problem is not everybody treats their dds the same exact way, and not every dil is in the market for a "2nd mum" (I know I wasn't). Plus, she may simply be trying too hard. Ugh!
Or maybe she was always like this. What does dh say?
I agree with other posters that one way to help ease this problem is to cut down the number of texts, etc. Also, I agree with agnurse about shortening the visits. I'm not sure I could survive one week with this woman, no matter how well-intended her behavior is - but 2 weeks? - blimey!
But none of that will change the way you feel about the touchy-feely stuff when she's there. You may have to tell her that you don't like being hugged by any but your nearest & dearest (or a better wording). And you may have to remove her hand when she starts stroking your head, and let her know you don't appreciate that.
On the flip side, perhaps she needs reassuring that she's going to be part of baby's life. You would think the pictures, etc. would do it, but she may need to hear it. Maybe find a moment to let her know that you want your child to have a good relationship with all his gps and that you're glad she and fil are in his life. But also let her know you, personally, need more space.
Other posters are right, in time, she may turn her affections more to your ds (sigh of relief). But if you see her overwhelming him with her attention/affection, you (and dh) will have to be prepared to stop that, too.