Need advice re neighbor

I live in an apartment complex that rents to many mentally retarded adults who are capable of living alone. They're really some of the best neighbors I've ever had, but I'm having a problem with one and don't know how to deal with it.

Barb is 61 years old, mentally about 10. Generally she's very sweet natured, but she gets her feelings hurt VERY easily. I've been a good neighbor to her, remembering her birthday, giving her home baked goodies at Christmas, including her in my family holiday dinners when she has nowhere else to go, and driving her here and there when she needs transportation.

Recently she's been dropping by 3 or 4 times a day, telephoning me half a dozen times a day, and inviting herself to dinner. It's become quite intrusive on my personal life. I can't constantly keep my shades drawn pretending to be asleep or not home, and I don't know what to say to her to control the situation without upsetting her and losing her as a friend.

Please give me some advice.

Maggie