“My Fiancee’s Mother is Very Pretty And She Has Been Eyeing Me These Days” Pls Should I?

The confused man narrated his story showing how his soon-to-be mother-in-law has become a scourge in his life.
Below is what he shared:
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My girlfriend and I are both 25 and we're engaged to be married next year.
She's an only child – her mum had her at 16 and then split up with the father soon after.
She never married, although has had several long-term relationships. She's single at the moment though.
My problem is that I think my mum-in-law-to-be is hitting on me. At first I thought I was imagining it, but I really don't think I am.
I've been dating my girlfriend for two years, but her mum only started flirting with me about six months ago after I redecorated her beauty salon for her (I'm a painter and decorator).
I saw her pretty much every day for about three weeks while the work was going on and, not that I want to blow my own trumpet, but I think she developed a thing for me.
Since then she's been very touchy-feely with me, uses any excuse to hug and kiss me, and is always making suggestive (but jokey) comments when we're all together.
My girlfriend hasn't said anything and I'm sure she'd probably laugh in my face if I told her what I think. But I feel uncomfortable and don't know what to do about it.
I should mention that her mum is pretty hot and all my mates fancy her. Should I tell my girlfriend, who's very close to her mum, or just ignore this unwanted attention?